Accuracy should trump easy-peasy

In January the ASME A112.14.3 sub-committee will once again meet to try to update the standard, which has remained unchanged since its publication in 2000.

One of the issues that the committee has struggled to come to consensus on is the incremental test cycles and the skim tank procedure.

At the risk of boring the reader to death - something I normally try to avoid - let me explain the procedure and the inherent problem that I believe needs to be addressed.

This is what the ASME A112.14.3 test apparatus looks like, conceptually anyway.

Once the flow rate is calibrated from the test sinks to the desired flow rate for the interceptor being tested, the testing procedure involves opening the drain valve on the test sinks and "let 'er rip".

The flow from the test sinks will pass through the grease interceptor and into the skim tank, after which any accumulated lard found in the skim tank is skimmed off (hence the clever and sophisticated name of the tank), dewatered and weighed. The weight of the lard taken from the skim tank is deducted from the weight of the lard introduced into the test sinks and the difference representing the efficiency of the interceptor during that specific test cycle.

Now, the skim tank is supposed to have a waste outlet connected to the bottom of the tank at one end and be trapped to retain approximately 18 inches of water in the tank. The tank is also provided with a four (4) inch bottom drain to permit draining and cleaning.

The purpose of the waste outlet being trapped to retain 18 inches of water in the tank is so that the tank volume does not drop below 18 inches during a test cycle.  In practice what this means is that the flow from the grease interceptor can actually pass through the skim tank during a test cycle since the waste outlet is typically not closed off during testing.

Is this a problem?

Perhaps not, but since the point of the testing procedure is to determine with the greatest accuracy possible the efficiency of a grease interceptor, this doesn't seem right to me.

In case you didn't quite follow all that, allow me to clarify the issue.

The skim tank is just that a tank intended to capture the effluent from the grease interceptor during a test run in order to measure the amount of lard that escaped the interceptor which will determine the efficiency of the interceptor.

If the tank is open during a test run it is possible for some of the lard that enters the skim tank to escape the skim tank.  Any lard which escapes the skim tank is automatically counted as lard that must be in the grease interceptor, which has the potential of reporting a higher than actual efficiency of the interceptor for a given test cycle.

Since the interceptor will be tested over a minimum of 13 cycles, the problem can be compounded resulting in a potentially significant higher than actual average efficiency for a certified grease interceptor.

The solution would seem to be a simple one; keep the skim tank closed during each test cycle.

I have proposed just such a radical idea to the committee before but have received resistance from some who cite the benefit of the "automatic" nature of the testing when the tank is allowed to remain open during each test cycle.

I take the term "automatic" to basically mean, "easy-peasy", which is actually short for "easy-peasy-lemon-squeezy", which means "very easy" and makes me think about vodka and a drink called a Lemon Drop...

I doubt that the proponent of the argument intended committee members to conjure up images of
alcoholic drinks, but I did anyway.

Further arguments have been proposed that at higher flows and a two-drop series (allowed by the standard) that a lack of  human intervention at the required time would cause the skim tank to overflow, invalidating the test.

It's hard to not respond with a bit of sarcasm to that argument, but I'll abstain and simply say, "hogwash".

The committee has already agreed to enlarge the size of the skim tank for testing grease interceptors at flow rates over 50 gpm.  The size of the larger skim tank will allow for two complete drops (test increments) at 100 gpm, which is 400 total gallons of water. There is no risk of overflowing the skim tank unless the "human interaction" fails to drain the skim tank prior to another test cycle.

If testing personnel fail to drain the skim tank down between two successive two-drop tests at 100 gpm, then I would agree that the test results would be invalid, requiring the interceptor to be tested over from the beginning - and the testing personnel fired for incompetence (after they clean up the mess, of course).

Anyways, it seems to me that accuracy in testing should be the most important issue - definitely more important that what's easy-peasy.

I'll update this post if any progress on the issue is made at the next committee meeting.

The 25% Rule; where did it come from?

Have you heard of the 25% rule?

In case you are unaware or have been off-planet for a while let me explain.

The 25% rule is used primarily by pretreatment authorities to determine when a grease interceptor (or oil separator) is full. A fairly universal definition would be:

"The total depth of the floating grease layer plus the settle-able solids layer cannot exceed 25% of the total liquid depth of the interceptor."

Determination is made by taking a core sample with something like a Sludge Judge or Dipstick Pro (I know of a few jurisdictions that use florescent light covers (clear plastic tubes) from Home Depot or Lowe's, with a rubber stopper).  The device is lowered slowly through the fats, oils and grease layer all the way to the bottom through the solids layer of the interceptor and then capped or plugged and slowly removed and set aside to rest.  This allows the captured FOG to collect at the top of the device while the solids settle at the bottom.

A measurement is taken, typically in inches, from the top of the FOG layer to the bottom of the device, which represents the tanks total water column.  Then the FOG and solids layers are each measured, also typically in inches, and added together.  If the combined FOG and solids layers are equal to or greater than 25% of the total water column then the interceptor is considered full.

For example lets take a typical gravity interceptor in the field like the one pictured here on the left. 

The technician is using a Dipstick Pro which appears to be showing a 48" water column and the technician is showing by the spread of his fingers a FOG depth of about 6" (okay, I'm guessing on that, but I have fairly large hands - not like Wilt Chamberlains, but I wear a large golf glove - and when I spread my fingers like his against a ruler its about 4.5" and adding a bit for the extra FOG above and below his fingers its about 6" or so, give or take).  If the solids layer at the bottom of the device is also 6" that would be a combined 12" of FOG and solids.  When you divide 12 by 48 you get 25%.

This particular interceptor is full, hence the stunned demeanor from the restaurant owner/manager as the technician gives him the bad news.

But wait, there appears to be quite a bit of space left in the interceptor for collecting even more FOG and solids, so how do we know that this interceptor is actually full (a question this restaurant owner/manager probably asked the technician)?

Here's the thing, it's not that the rule is a scientifically based determination of efficiency breakdown, or that the EPA has mandated it, it's more like a generally accepted rule-of-thumb that many jurisdictions have adopted.

Where did it come from?

Good question.

I've been looking for the answer for a while now and no one seems to know.

Seriously.

In 2011, while preparing for a presentation at the Pacific Northwest Grease Summit in Bellevue Washington, I wondered if there was a correlation between the capacities of certified hydromechanical grease interceptors and the 25% rule.

I took all of the major manufacturers certified units (JR Smith, Zurn, Mifab, Watts, Josam, and Wade) and did some very basic math.  For example, if a unit was certified at 20 gpm with 40 lbs grease capacity using lard, I converted the amount of lard in the interceptor, when it was full, into gallons and then divided that by the amount of water the unit could hold.

It didn't matter which manufacturer's unit I checked, the results were very similar and all within a narrow range.  The maximum capacity for storing grease before failure in each unit I checked was between 25% and 35%.

This is further supported by the Plumbing and Drainage Institutes 1998 (R-2010) paper Guide to Grease Interceptors - Eliminating the Mystery, in which they stated that PDI-G101 certified interceptors may need maintenance when as little as 25% of their rated capacity has been reached.

Fast forward to my more recent research in which I have been emailing jurisdictions, googling the internet and searching all available forums for any clue as to the origins of the 25% rule.

Honolulu appears to be one of the early if not earliest users of the rule.  A post on the Yahoo Pretreatment Coordinators forum said that the jurisdiction did the same calculations as far back as 1995 as they were developing their FOG program.  It was stated that the jurisdiction chose 25% to be conservative and it became the rule for grease interceptor maintenance enforcement in their new FOG program.

Many of the jurisdictions in Orange County California use the 25% rule based on a recommendation in the Orange County FOG Control Study which was not based on any science, but rather on a survey of FOG control programs around the US, many of which were using the 25% rule or similar standard such as maximum inches of accumulation of FOG or solids.

The 25% rule appears to be ubiquitous in FOG programs and ordinances, not because of any scientific or technical merit, but rather it seems to have its footing in the idea that 'everyone else is doing it' so it must be right.

The problem now is that the rule is well entrenched in these FOG programs and ordinances making it difficult for jurisdictions to be flexible with newer technologies that hold more grease in comparable foot prints to traditional designs, in some cases matching the storage capacities of much larger gravity style interceptors.

Schier Products Great Basin, Thermaco Trapzilla and other products looming on the horizon are capable of storing grease and solids to well over 50% of their liquid volume, but jurisdictions are challenged to figure out a way to allow an owner to actually benefit from these higher capacities, owing to limitations set on themselves through enacted policy.

Hopefully by understanding how we got where we are, jurisdictions can gain insight into how to either avoid the pitfalls in setting universal capacity limits and/or perhaps, correct any problems that may have been created in enacted policies that inadvertently punish owners who would choose to use newer more efficient higher capacity technologies.

Anyone out there that has more information on the history of the 25% rule please message me and I'll update this post. 

Grease Production Sizing

Although sizing grease interceptors, whether gravity or hydromechanical, has always been based solely on flow rate, this strategy falls short in that it does not consider how much grease a specific food service facility could produce.

There are many times when volume or flow rate sizing would lead to the same size interceptor for a subway sandwich shop as for a Mexican grill, however it is well understood by inspectors that these two types of restaurants produce significantly different amounts of fats, oils and grease (FOG).

Schier recommends using a grease production calculation to determine how much grease a particular restaurant is likely to produce in order to ensure that the specified grease interceptor has sufficient grease storage capacity to allow for a realistic and affordable pump out frequency.


 

We developed the above categories for restaurants based on feedback from jurisdictions and pumper contractors around the country, combined with reports such as the Brown Grease Study (Kennedy Jenks 2011) which gives detailed information about restaurant types and menu's as well as grease and solids production data.

The formula for calculating grease production requires three bits of information:
1. Grease production per meal - you simply have to decide by menu type which category (low, medium or high) that the restaurant falls under and then whether the restaurant uses flatware or disposable (plastic or paper) forks, knives, spoons, plates, cups, etc.

2. Meals or customers per day - if this is a franchise they typically have this information available. Independent start-ups may not know this information up front, in which case you may have to make an educated guess or phone a friend or consult a medium. Most of the time you can get close enough that the calculation makes sense.  Just remember that its better to err on the high side.

3. Days per pump-out cycle - this is simply the maintenance cycle you plan to use for pumping out the interceptor.  Most people will not maintain an interceptor that is sized to be cleaned out more often than once per month and most jurisdictions won't let an interceptor be maintained less often than once every 90 days.  Somewhere in between is the sweet spot for your project.

The formula for calculating grease production is very straight forward. You simply take the amount of grease expected per meal (a,b,c,d,e, or f), times the number of meals expected per day, times the number of days between pump outs to arrive at the grease capacity required for the interceptor.

Lets take a couple of real-world examples:

Example 1
McDonalds (medium grease producer, no flatware - category "c")
400 meals per day X 0.025 lbs per meal = 10 lbs FOG per day, or 300 lbs every 30 days, or 600 lbs every 60 days, or 900 lbs every 90 days.

You can also take a grease interceptors' certified capacity and divide it by the amount of grease production per day, to determine the pump out frequency as follows:

10 lbs per day would require:

Schier GB-75, 75 gpm, 616 lbs = 61 days between pump-outs
Schier GB-250, 100 gpm, 1076 lbs = 108 days between pump-outs
Trapzilla TZ-400, 75 gpm, 400 lbs = 40 days between pump-outs
Trapzilla TZ-600, 75 gpm, 600 lbs = 60 days between pump-outs
Mifab BigMax 750, 75 gpm, 150 lbs* = 15 days between pump-outs
Mifab BigMax 1150, 100 gpm, 200 lbs* = 20 days between pump-outs

*based on grease interceptors' actual third party certification (not based on the manufacturer's claims of performance, which cannot be proven).

Example 2
Buffalo Wild Wings (high grease producer with flatware, category "f")
642 meals per day X 0.455 lbs per meal = 29.2 lbs per day, or 876 lbs every 30 days, or 1,752 lbs every 60 days, or 2,628 lbs every 90 days.

29.2 lbs per day would require:

Schier GB-75, 75 gpm, 616 lbs = 21 days between pump-outs
Schier GB-250, 100 gpm, 1076 lbs = 36 days between pump-outs
Trapzilla TZ-400, 75 gpm, 400 lbs = 14 days between pump-outs
Trapzilla TZ-600, 75 gpm, 600 lbs = 20 days between pump-outs
Mifab BigMax 750, 75 gpm, 150 lbs* = 5 days between pump-outs
Mifab BigMax 1150, 100 gpm, 200 lbs* = 7 days between pump-outs

Of course you can increase capacity by increasing the number of interceptors in order to lengthen the pump-out cycle, i.e:

Schier GB-250 (2), 100 gpm, 2152 lbs = 74 days between pump-outs

Using the grease production sizing method is not limited to any specific manufacturer, you can use it for any interceptor.

The only thing to watch out for is the funny-business some manufacturers' play in making unsubstantiated claims of capacity that they want to be used in determining a pump-out frequency.

Sorry Charlie, that's just not going to work.

When in doubt ask them for their certified test reports to see what their actual/real/genuine/true/factual capacity is, then base the pump-out cycle on that.

High Capacity Hybrid HGI Replacement of 1000 Gallon GGI

Replacing a large volume gravity grease interceptor is expensive and time consuming.

Owners like Chipotle Mexican Grill are opting for better performing high-capacity hybrid hydromechanical (HGI) grease interceptors such as Schier's Great Basin series to replace failing concrete gravity interceptors at locations such as this in Belton MO.

This 1000 gallon concrete interceptor is just 11 years old:



https://www.youtube.com/watch?v=Y6Cz3KL838o&feature=youtu.be

Grease interceptors are not called traps anymore

Every now and again the question of whether a grease interceptor is still considered a trap comes up. 

Grease interceptor...grease trap...you say tomayto, I say tomahto - does it really matter?

The distinction is important enough that you should be on the lookout for a fearsome predator known as a lawyer.  These anal-retentive-jot-and-tittle-semantics-fanatics have already picked up the scent of blood in the water on this subject.

Disclaimer: the sharks in suits pictured here are not intended to represent any particular lawyer or lawyers; any similarity to actual individuals is purely coincidental.

Anyways...

It's interesting to see how the Uniform Plumbing Code (UPC) and the International Plumbing Code (IPC) have evolved on this issue over time.

UPC
Through the year 1997, the UPC mandated that grease traps have a 2" water seal (the minimum required for a fixture trap), allowed a maximum connection of four fixtures and allowed the grease trap to be used as a fixture trap for a single fixture provided that the distance between the fixture outlet and the grease trap did not exceed 4 feet and the vertical tailpipe or drain did not exceed 2-1/2 feet. 

In 1994 the UPC added or clarified a restriction by stating that, "no fixture shall be double trapped," which created a conundrum. Since the code prohibited double trapping fixtures, and since a grease trap was allowed to serve up to 4 fixtures, if the grease trap is considered a "trap" owing to its 2" water seal, and it can serve as a fixture trap for a single fixture, and it can receive the discharge of up to 4 fixtures, and each of those fixtures must be individually trapped, and each of those fixtures is then routed to a grease trap, then all 4 fixtures are double trapped, which is a violation of the code.

The 2000 UPC eliminated some confusion by removing the language that allowed a grease trap to serve as a fixture trap as had been previously approved and eliminated the requirement for a minimum 2" water seal. Yet this really only added confusion since a grease trap would no longer be required to have a water or trap seal but it was still called a trap.

The 2006 UPC eliminated the term grease trap and introduced a new term, hydromechanical grease interceptor (HGI), to define passive grease interceptors. By eliminating the term grease trap and all references to it, and by not allowing a HGI to serve as a fixture trap for even a single fixture, the UPC eliminated the confusion that had existed over whether a grease trap was a trap.

It's not.

IPC
Prior to 2006 the IPC defined grease interceptors and grease traps, which were distinguished from each other only in that a grease trap had a rated flow of 50 gpm or less while a grease interceptor had a rated flow exceeding 50 gpm. A grease trap intended to serve as a fixture trap in accordance with the manufacturer's installation instructions was permitted to serve as the trap for a single fixture or a combination sink of not more than three compartments so long as the vertical distance from the fixture outlet to the inlet of the interceptor did not exceed 30 inches and the developed length of the waste pipe from the furthest compartment outlet to the inlet of the interceptor did not exceed 60 inches (1002.1 Exception 3).

In 2006 the IPC removed the definition for grease trap and changed the definition of grease interceptor, removing any reference to rated flow, making it the term for a passive grease interceptor.  The code language under 1002.1 Exception 3 from previous codes was not amended, retaining the term grease trap, a term which was no longer defined in the code.

The 2009 IPC removed all references to the term grease trap. The code language under 1002.1 Exception 3 was amended, changing the term grease trap to grease interceptor.

The 2012 IPC introduced a new definition of grease interceptor adding two new terms; hydromechanical and gravity.  The term hydromechanical grease interceptor (HGI) was introduced as the new term for a passive grease interceptor while the term gravity introduced a liquid volume-retention time based type of interceptor.  Beyond simply defining the term, the code made no further reference to gravity grease interceptors.  Section 1002.1 Exception 3 remained unchanged.

The 2015 IPC added another subcategory for grease interceptors called fats, oils and grease (FOG) disposal systems and added section 1003.3.6 governing gravity grease interceptors and the new FOG disposal systems. Section 1002.1 Exception 3 remains unchanged. 

The problem I see with the IPC is in the misapplication of a HGI because the section doesn't require the interceptor to have a 2" water seal.  Instead it relies on the manufacturer to stipulate that the interceptor is intended to be used as a fixture trap in compliance with the language of the section. 

That's dangerous to me. 

By dangerous of course I mean like wearing tuna-laced swim trunks and swimming in shark infested waters.

The IPC could eliminate the confusion by simply requiring a 2" water seal for any interceptor approved for installation under section 1002.1 Exception 3.

Time for someone to submit a code change proposal for the next code cycle...anyone?

Plumbing Codes and Pretreatment Ordinances

One of the biggest challenges in the evolving world of grease interceptors is understanding the roles of plumbing codes and pretreatment ordinances.

The plumbing code and its inspectors are the watchman over the plumbing systems in commercial and residential building construction.

The pretreatment ordinance and its inspectors are the watchman over the wastewater collection
system.

In the vast majority of jurisdictions in the US the pretreatment ordinance supersedes the plumbing code in authority where a conflict between the two exists.

When it comes to grease interceptors the plumbing code has been mandating their use and governing their approvals since 1946, whereas pretreatment authorities have only more recently gotten involved with them.


This has created an interesting dilemma; pretreatment ordinances are concerned with the quality of the wastewater entering the collection system while plumbing codes are concerned with setting a minimum standard for the construction of a plumbing system.

Are these issues at odds with each other?

Yes, in a way.

Amendments to the 2011 Oregon Plumbing Specialty Code (OPSC) (effective January 1, 2013) illustrate the disconnect between the plumbing code and pretreatment ordinances.

Lets say you are a municipality in Oregon operating under an NPDES permit issued by the EPA mandating you to implement a program to reduce sanitary and combined sewer overflows in your jurisdiction. 

Lets say you go out into your community and begin inspecting restaurants to see what they are doing to mitigate the discharge of fats, oils and grease to your collection system.

Lets say you discover they have a lot of grease build-up in the laterals leading to your collection system.

Lets say you discover that a significant number of these facilities either have no grease interceptor or have an undersized interceptor serving their multi-compartment sink and they are not maintaining it very well or very often.

Lets say you also discover a significant amount of grease discharging through fixtures that are not even connected to the grease interceptor.

Lets say you talk to the plumbing plans review and permitting department and they tell you that they just, "follow the state plumbing code."

Lets say that you read the state plumbing code and discover the following language, "Where it is determined by the Authority Having Jurisdiction (you, in this story) that waste pretreatment is required, an approved type of grease interceptor(s) complying with the provisions of this section shall be correctly sized and properly installed in grease waste line(s) leading from sinks and drains...where grease is introduced into the drainage or sewage system in quantities that can effect line stoppage or hinder sewage treatment..."

Lets say you tell the plans reviewer and permit issuer that you want them to require all fixtures in a commercial kitchen be routed to a grease interceptor and lets say they don't agree with you (because they haven't investigated the discharge of fats, oils and grease from these kinds of facilities and aren't aware of the problem you are trying to address).

This would be the point at which you learn that, in Oregon, you don't have the authority to make such a requirement because of this little clause in ORS Chapter 455 Building Code, Section 455.040, "The state building code shall be applicable and uniform throughout this state and in all municipalities, and no municipality shall enact or enforce any ordinance, rule or regulation relating to the same matters encompassed by the state building code but which provides different requirements unless authorized by the Director of the Department of Consumer and Business Services."

This is very much what happened in Oregon.

Fortunately, stakeholders were able to sit down and discuss the problem which ultimately led to an amendment to the state plumbing code that now reads, "Waste pretreatment is required in all Food Service Establishments...The following plumbing fixtures and drains shall be connected to the grease interceptor(s): All plumbing fixtures, garbage disposals, dish-washers, floor drains, and cooking equipment, with drain connections in food and / or beverage preparation areas of all Food Service Establishments."

This amendment was only possible because plumbing code officials were open to the idea that the plumbing code should support pretreatment program compliance requirements.


Of course ultimately this needs to be done nationally which will require amending plumbing codes such as the Uniform Plumbing Code, the International Plumbing Code as well as the various state plumbing codes to make them more effective and supportive of pretreatment programs.

Effective FOG abatement requires a team effort that includes comprehensive pretreatment ordinances supported by effective plumbing codes.

Oregon provides a case-in-point regarding the disconnect that often exists between plumbing codes and pretreatment program compliance requirements, but also a model for resolution that benefits everyone.

Bernoulli's Principle Revisited

One of the most popular posts I have written deals with the question of whether Bernoulli's Principle is behind the operation of hydromechanical grease interceptors, as some have argued.

The specific point I was making in that post (Is Bernoulli's Principle Behind Grease Interceptor Performance?) is that there is no evidence that deliberately adding baffles to the interior of an interceptor (to create regions of higher and lower pressure) enhances grease separation.

Gravity differential separation works best in a laminar low-velocity flow environment.

Attempting to enhance the natural separation of liquids with differing specific gravities by incorporating regions of higher and lower pressure by means of internal baffles, doesn't even make sense.

It would be like hooking your car up to a team of horses to add some "horsepower."

I guess technically the horses add horsepower, but do you really think the car is going to go faster!

So why am I writing about Bernoulli's principle again?

Because, there is a proper application of Bernoulli's Principle in grease interceptor design.

Lets begin with a couple of basic concepts in fluid hydraulics.

Liquids are generally non-compressible, which means you cannot change the volume of a liquid by adding pressure. 

The 'conservation of mass' principle requires every bit of mass (volume of liquid) to be accounted for during a process.

Think of a water hose with a spray nozzle attached.  As you close the nozzle the stream tightens up and goes farther.

The tighter the stream the higher the velocity (the speed at which the liquid is moving).

Since neither the mass nor the volume can change under steady-flow conditions, the velocity must change to allow the mass and volume of liquid to move from the larger area in the hose through the smaller area in the nozzle.

When I was a boy, my brothers and I discovered the awesome power of the tight stream from a hose nozzle which could clean dirt and mud from almost anything.

We often tried to clean each others faces off with this same technique - which invariably led to an opportunity to sit quietly for a while to contemplate our "actions".

I took contemplate to mean ponder all the ways to blame my brothers for the trouble we were in, while plotting appropriate avenues of revenge. 

Anyway, what does this have to do with grease interceptors?

The same is true in reverse!

Think of the nozzle as being the waste piping connecting to a grease interceptor.  The volume and mass of liquid is constant but the velocity changes as the liquid moves from the pipe through the interceptor.

Good interceptor designs will take the mass and volume of water and distribute it throughout the cross-sectional area of the interceptor to reduce the velocity - the speed at which the volume is moving through the interceptor - allowing for gravity differential separation (The real difference between Gravity and Hydromechanical grease interceptors).

Now it may be easier to understand why adding baffles inside the interceptor would not make sense.

The baffles add an obstacle inside of the interceptor that the liquid must flow around.  Velocity increases as the liquid moves around the edges of the baffles and while there is an associated pressure drop, the increase in speed and turbulence more than compensate for the pressure drop making it more difficult for gravity differential separation to occur.

Proof?

If you promise not to get mad, I'll demonstrate the point by comparing several PDI certified 20 gpm units to Schier's GB-20:

Yes, the Schier GB-20 holds more water than the other units.  That's why we are looking at lbs per gallon to compare each interceptor's efficiency in capturing and storing grease.  It simply illustrates that the baffles in these PDI certified units do not enhance the interceptors performance.

The Schier unit has no internal baffles - it's wide open. It does a better job of distributing the volume of liquid throughout the units cross-sectional area which reduces velocity and enhances separation.

So now you can rest easy - feel free to even snore a bit - knowing that Bernoulli's principle does figure into good grease interceptor design - just not the way you might have thought.

What's Wrong with Semi-Automatic Draw-Off?

The contents of a grease interceptor, especially one that has not been cleaned out recently, is nothing short of breathtaking!

By 'breathtaking' of course I mean one whiff makes your eyes water and gives you the kind of nausea common on commercial fishing charters, while you reel backwards in a desperate fight for oxygen...and a gas mask.

I had the same experience one time when I accidentally smelled one of my teenagers dirty socks.

It's the kind of experience you are not likely to forget and if you are a restaurant owner it's one you are not likely to repeat - at least very often.

As the saying goes, "necessity is the mother of invention," and not opening a grease interceptor is considered, at least by some, a necessity.  

Enter the semi-automatic draw-off grease interceptor, which as one manufacturer's literature states, "permits removal of accumulated grease without cover removal."

Yeah baby, the holy grail of indoor grease interceptors, right?!

Not so fast.

Here are two major reasons that semi-automatic draw-off is not the right solution:


1. Typical cleaning instructions:

• Run full stream of hot water (preferably 140 deg F or higher) for at least two minutes
• Turn off hot water for three to five minutes - to allow grease to liquify
• These interceptors come with a shut-off valve connected to the outlet - step three is to close the shut-off valve
• Most units come with a draw-off valve on top connected to a hose or pipe - step four is to open this valve and place a container under the hose or pipe
• Now run hot water through the unit at 1.5 to 2.5 gpm causing the unit to fill, raising the accumulated and now liquified grease into an internal cone and out the draw-off connection
• Continue to run the hot water through the interceptor until clear water appears then shut off the flow
• Close the draw-off valve and open the shut-off valve and the interceptor is now supposedly clean and ready for use again

As an owner you have to do this process each and every time you service the interceptor.  How many full buckets of the interceptor's contents - which, by the way contain the very odor the owner was hoping to avoid in the first place - would it take for the owner to give up ever wanting to service the interceptor again?

Another thing to consider is that some places employ teenagers whom will be tasked with this job.

Teenagers!

I raised three of them myself and I can tell you, based on my experience trying to teach them to make their beds every day, that I have grave concerns about trusting them to properly follow the instructions above...ever.

If you are a teenager reading this post and you feel that my comment does not apply to your bed-making skills then I apologize for lumping you in with my kids, and basically every other teen that has ever been born.


2. How are accumulated solids removed?

It is a well established fact that grease interceptors collect solids, which have to be removed regularly because they decompose inside the interceptor creating all kinds of problems not the least of which is the unforgettable odor I mentioned earlier.

To remove the solids you have to remove the cover, which should cause you to stop and think, "hey, wait a second, why would I want a semi-automatic draw-off if I have to take the cover off the interceptor to clean out the solids anyway?"

Exactly!

So what is the right application for a semi-automatic draw-off?

Let me see, that would have to be a restaurant that does not serve food of any kind and that does not employ teenagers whom would be tasked with the responsibility of maintaining the interceptor and that has an owner that doesn't mind bucket full after bucket full of the interceptors contents stinking up the joint.

So, doing the math, there are approximately 990,000 restaurants in the US according to the National Restaurant Association, and the total number that do not serve any food of any kind would be roughly 0.1% or about 990.  Of those, the number that do not employ teenagers or that have a masochistic owner would be...lets see...divide by...carry the zero...

We're working with very small percentages here, but I think the answer is one.

Whatever the number is, it is too small to justify the existence of the semi-automatic draw-off.

For most restaurants, there is a better way.

A High-efficiency and high-capacity grease interceptor installed outside with all of the kitchen fixtures routed to it, properly sized and properly maintained is the real solution!

ps. teenagers make great restaurant employees, just don't expect them to make their beds every day, or really ever.

LEED points for Grease Interceptors?

Dear plumbing and/or mechanical engineer and loyal interceptor whisperer fan,

By 'fan' of course I mean anyone who has ever read one of my blog posts OR just accidentally stumbled upon the blog and didn't immediately hit the back button OR after hitting the back button, later recalled, even if somewhat vaguely, having ever visited the blog - really the definition is a bit fluid right now.

Anyway, now that we have firmly established with whom this particular blog post is concerned, let us move on to the increasingly more important topic of building construction and the LEED certification program.

Now, if you are not aware of what LEED certification is then you are most likely not the intended reader of this post. That being said, for those who do not know what LEED certification is but who would like to read this post anyway - I am concentrating very hard right now and meditating deeply upon whom that might be and really, no one comes to mind - you may find more information here: http://www.usgbc.org/certification.

If you would not like to read further but would like to know what the audible equivalent to reading further would be, click here: https://www.youtube.com/watch?v=vWuQVpBeqLs

Now then, back to those who already know what LEED certification is.  The point of this post is to answer a question that comes up from time to time, "are there any LEED credits for particular grease interceptors?"

It is at this point that I would normally indulge a masochistic need to share the minutia of the LEED certification credit system to satisfy myself that I have thoroughly analyzed and answered the question regardless of how you, the reader, feels about it.

I believe, however I can reduce all of that extra typing and the resulting exacerbation of carpal tunnel syndrome by answering the question as follows:

NO!

On the off chance that there may be someone out there not completely satisfied with that answer, allow me to point out the relevant portions of the LEED 2009 for New Construction and Major Renovations Rating System that bear on the question.

Materials and Resources
There are three possible subheadings that would potentially apply to grease interceptors.  They are:
MR Credit 3: Materials Reuse
MR Credit 4: Recycled Content
MR Credit 5: Regional Materials

Each of these credit areas make the same statement, which I believe will satisfy even the most meticulous student of LEED certifications:

"Mechanical, electrical and plumbing components and specialty items such as elevators and equipment cannot be included in this calculation."

So there you have it, grease interceptors do not qualify for LEED credits.

Whether you are a first time reader or in the off chance you have returned deliberately to this blog (i.e. you are a fan), I hope this in-depth review and insightful post prove helpful should the question of LEED credits and grease interceptors ever come up around your office.

Understanding Rated Grease Capacity versus Maximum Grease Capacity

The grease interceptor revolution is about challenging the status quo.

It's about asking tough questions and thinking radically different about the answers.

It's about listening to the people who are affected by the products we make.

The revolution is about making High-capacity grease interceptors because contractors, engineers, restaurant owners and jurisdictions are demanding superior performance.

As more manufacturers see the light and join the revolution it's important that you understand what to look for to make sure that an interceptor that claims to be high-capacity really is high-capacity.

The journey to enlightenment begins with an understanding of the testing and rating requirements of both nationally (US) recognized and plumbing code approved standards and ends with an understanding of some of the tricks of the trade used to disguise an interceptors performance to make it appear to be something that it is not.

Testing and rating requirements

In most jurisdictions across the US, hydromechanical grease interceptor's must be tested and rated to either PDI G-101 and ASME A112.14.3.

Both standards are similar in most respects including the same testing and rating protocol, however there is a key difference between them; PDI allows for either Rated Grease Capacity (RGC) or Maximum Grease Capacity (MGC), while ASME currently only allows for MGC.

What's the difference between RGC and MGC?

An interceptor certified to MGC has actually been tested all the way to its breakdown point while an interceptor tested to RGC has not.

Let me quote from PDI G-101 so you can see the difference between the two ratings:

7.6.2 Determination of Test Breakdown Point (Maximum Grease Capacity)

The test failure, or breakdown point of the interceptor, shall be established at the increment preceding two (2) successive increments in which either the average efficiency is less than ninety (90) percent or the incremental efficiency is less than eighty (80) percent.

7.7 Efficiency Determinations (Rated Grease Capacity)

The grease shall be removed from the skimming tank and the efficiency of the interceptor shall be computed at the (13) thirteenth increment. This provides at least a twelve and one-half (12.5) percent safety factor on the ratio of the rated grease retention capacity to flow rate as indicated in Table 1:



To put the difference between RGC and MGC into perspective lets review the actual test data from NSF for Schier Product's GB-250:




You can see at the 13th increment the GB-250 had an average efficiency of 95.2% and had separated 247.46, which under PDI would allow it to be certified at 200 lbs grease storage capacity according to Table 1.

Under ASME A112.14.3 (which this unit is certified to) there isn't an option for RGC so you have to test to failure (prior to 2007 this wasn't an option under PDI either).

As you can see the GB-250 suffered two successive increments (59 and 60) with incremental efficiencies below 80%. The test breakdown point (the increment that is to be used for certification of the interceptor) is increment 58 at which the GB-250 had an average efficiency of 92.8% and separated 1076 lbs of grease at 100 gpm.

The revolution is gaining momentum

As I said earlier, other manufacturers are apparently starting to see the light.

As new products emerge to compete in the arena of high-capacity grease interceptors though, it's important not only to know how grease interceptors are rated, but also how a manufacturer reports their ratings.

Tricks of the trade

How do you know if the grease capacity shown on a specification or submittal sheet is the interceptor's actual certified capacity or an unsubstantiated claim?

To be honest it can be difficult.

One manufacturer uses the term Grease Design Capacity to confuse or imply that this is the interceptors actual certified capacity. An investigation into the testing and rating of the interceptor revealed that it was certified as RGC, which means the interceptor wasn't tested to failure and therefore their posted 'design' capacity is uncertified and unsubstantiated.

One manufacturer uses the term Greasy-Sludge Capacity. What does that mean? I'm not sure. The amount listed is more than their certified grease storage capacity. The number appears to be a combination of grease and solids capacities combined. But since neither PDI nor ASME test for solids there is no way this number can be substantiated.

Another manufacturer doesn't use pounds at all, instead opting to show their grease capacity in gallons. When you take the gallons and convert it into pounds, you end up with a lot more claimed grease capacity than their apparent certification.

When in doubt ask for the test report.

At the end of the day there is really only one way to know what the actual grease storage capacity of an interceptor is and that is to ask the manufacturer for the test reports.

In case you were wondering, testing agencies are not obligated to share the certification reports for any of their manufacturer's (I was informed of this in a very lawyer-like manner when I asked). That means you have to ask the manufacturer themselves.

Both PDI and ASME require interceptor tests to be documented on Test Form #1, which records each and every test increment along with incremental and accumulated efficiencies. The test report will tell you whether the interceptor was tested only to 13 test increments and is therefore rated at RGC or if the interceptor was tested to failure and you can see for yourself the interceptors MGC.

Schier Products believes wholeheartedly in the interceptor revolution and as such is working on posting the NSF test reports for each certified unit on its website here : http://www.schierproducts.com/Grease%20Interceptors%20Great%20Basin.html. In the mean time, if you would like to see a test report for any of Schier's certified units, just send me an email and I'll get them to you right away.

Competition is a good thing and manufacturers who want to join the revolution are welcome, but now you know what to look for to be sure that the interceptor that claims to be high-capacity really is high-capacity.

The Grease Interceptor Revolution

They say that imitation is the sincerest form of flattery, which sounds good to me, although I'm not sure who 'they' is.

If it's true, then the Schier team should be blushing, based on whats been happening in the world of grease interceptors recently.

Let me explain (or as Ricky Ricardo used to say, "esplain").

Schier Products is leading a grease interceptor revolution!

Prior to 2006, when Schier launched the Great Basin series, there had been little change in the way grease 'traps' were manufactured and certified. 

Prior to the year 2000, the only standard governing these devices was PDI G-101, which was originally published in 1949 and was based on research conducted at the Iowa Institute of Hydraulic Research (IIHR) in the early 1940s.

Even before the PDI standard was launched, the IIHR had been conducting testing on grease interceptors and had developed a rating system.  Any type of grease interceptor, before it could be installed in an army camp kitchen, had to have a rating certificate from IIHR.  

The image to the left is a schematic of the IIHR test apparatus.  

What was significant about the testing and rating that had been developed at the IIHR was the initial focus on army camp kitchen installations.

It was the army which had requested a standard that could be incorporated into its specification for grease interceptors, MIL-T-18361 (cancelled in 1982), because in the absence of a standard, ratings were determined by each manufacturer for their own interceptors.

IIHR Certified interceptors were required to meet the following minimum performance standards under the test parameters:

• Must have a minimum 90% average efficiency
• Must separate and store 2 lbs of grease for each gpm of flow at the minimum average efficiency.

Since the focus of the research was grease interceptor sizing and rating for army camp kitchens, the researchers created Table B (at right) listing the type of fixtures and recommended minimum rate of flow capacity for any interceptor that would be connected to those fixtures.

This created a problem.

It placed emphasis on how much flow an interceptor could receive while meeting the minimum efficiency and storage capacity requirements.

At left is a typical laboratory test data report for a commercial grease interceptor tested by IIHR.

Notice that the interceptor was tested to failure at multiple different flow rates!  

Why is that?

The goal was to test the interceptor to find the maximum flow rate that the interceptor could be certified to, while meeting the minimum requirements for efficiency and grease storage capacity.

How is that any different than today?

As I said earlier, when it comes to grease interceptor technology, until more recently things were operating pretty much exactly the same.

In 2000 ASME published an alternative standard for grease interceptors, ASME A112.14.3, but unlike the PDI version, this new ASME standard was consensus based and much more flexible with innovative technologies while still requiring the same performance testing as PDI G-101.

The advantage of the ASME standard is that, unlike PDI, a manufacturer does not have to use a vented external flow control and air entrainment as mandated by PDI. Instead, ASME allows for non-vented external flow control, integral (or built-in) flow control, or even an indirect connection.  

At last, an industry recognized and approved standard that lets manufacturer's innovate their interceptor designs to create better performing technology.

Prior to the launch of the new Great Basin series, Schier's R&D team took a radically different view of grease interceptor design based on the flexibility offered under ASME A112.14.3:

• Why create an interceptor that merely meets the minimum performance requirements in the standards?  
• Why not create a design that has a higher average efficiency than 90%?  
• Why not create a design that can hold five or 10 lbs of grease for each gpm of flow rate?  
• What happens to lemmings?

This thinking led Schier to designs that had substantially higher efficiencies and storage capacities than traditional PDI G-101 certified interceptors.  

Schier has certainly not been alone in the revolution!  

Thermaco's Trapzilla grease interceptors have been available for several years and also dramatically outperform traditional PDI G-101 certified interceptors.

Whats finally happening now is that other manufacturer's have 'seen the light' and are introducing certified interceptors intended to compete with Schier's higher effiencies and storage capacities.

While competition is good for the industry, not all competition is the same. 

What is 'design capacity'?  Why do some manufacturer's list different grease storage capacities on the same specification sheet?  Why do some manufacturers use their own terminology instead of recognized industry terms for grease and solids capacities? How do you know how a grease interceptor actually performed during testing?

I will address these questions and more in my next post on grease interceptor testing and ratings - Understanding Rated Grease Capacity versus Maximum Grease Capacity. 

When you know and understand the testing and rating systems in approved standards and what to look for in a certification you'll be better informed when specifying or approving a grease interceptor.