What is two-step sizing for grease interceptors is a common question I am asked. Uniform Plumbing Code (UPC) sizes hydromechanical grease interceptors (HGI) by flow rate (pipe size) as shown in step 1 above. If you are using a 4" grease waste line on a project UPC would require a minimum 75 GPM HGI (2-minute drain time) such as the Schier GB3. The GB3 is a third-party certified 75 GPM HGI so code is satisfied, right?

Technically yes, but the shortcoming of stopping at step 1 is that it does not factor loading. Compare two similar restaurants, let's say they are similar in size, kitchen equipment, the number of meals served per day (let's say 300) but the difference is food type. Restaurant 1 is a sandwich shop and restaurant 2 is a bar and grille. Back to the GB3 that satisfied UPC. The GB3 is third-party certified to a maximum grease capacity of 175.6 lbs of grease separated and stored. The sandwich shop would be considered a category A in step 2 above and produce 0.005 lbs of grease per meal served. 300 meals served per day * 0.005 lbs per meal served = 1.5 lbs of grease produced per day. By comparison the bar and grill at 300 meals served per day * 0.0455 lbs per meal served = 13.65 lbs of grease produced per day.

See the problem with stopping at step 1? If the GB3 is used it will require maintenance every 117 days at the sandwich shop (175.6 capacity of GB3 / 1.5 lbs grease produced per day). The bar and grill every 12 days (175.6 / 13.65). Both are UPC compliant per step 1 but by not considering loading they yield two very different maintenance intervals. 

The solution? The Schier GB-250 is 100 GPM, satisfies step 1 as it's 75 GPM or larger but will separate and store 1,751 lbs or grease. By using a GB-250 in the bar and grill application we can match the maintenance interval of the sandwich shop. 1,751 lbs grease capacity / 13.65 lbs produced per day = 128 days between cleanings. 

That's the basic concept of the two step approach. To make this really easy Schier has an online sizing program Grease Monkey that will allow you to input all parameters of the job and give a recommendation. They even have a team that will pre-approve AHJ acceptance and it's free.

Try out Grease Monkey today >>

With 510 gallons of capacity the GB-500 slots perfectly between the successful 275 gallon GB-250 and the new 1,010 gallon GB-1000. Available early 2019 the GB-500 is third-party certified to ASME A112.14.3-2018 to hold 3,048 lbs of grease. The GB-500 can be installed above or below grade and has a new riser system allowing up to burial depths of 8' (top of unit to grade). A few firsts for the GB-500 is also the new triple inlet and outlet design allowing for ultimate design ease as well as the Safety Star™ feature preventing accidental entry into the tank. More about the GB-500 can be found here >>

I've been asked this same question many times and Ken Loucks of IW Consulting Service provides a great explanation. If you aren't part of his email list sign up.  Read more here >>

Schier Products recently unveiled the latest version of their grease interceptor sizing service, Grease Monkey. Updates include the ability to create a profile and save jobs for future reference or use, the ability to do a quick sizing and a polished user interface that makes determining what product you need for your job easy. Grease Monkey uses Schier's grease production sizing method to determine real world demand based on volume and food type all while adhering to UPC guidelines. 

Try it out now >>

I'm asked often by engineers should a hose bib be placed near an indoor grease interceptor and the answer is yes.  Hot water is preferable but cold will do if thats all that is practical for the design. During the cleaning process the pumper will remove the FOG and solids that have accumulated since the last cleaning and while the tank is empty best practice is to spray down the interior walls and diffusers of any remaining material. 

<< Jimmy Johns in Ballard, Washington - Above grade install of GB-75 located in corner of attached parking garage

If you specify grease interceptors and aren't familiar with the Interceptor Whisperer, you should be. The blog created by IW Consulting answers many common questions regarding interceptor history, technology and best practices. 

Should a floor drain, floor sink or dishwasher be connected to a grease interceptor? Read about it on the IW blog post: https://www.iwconsultingservice.com/single-post/2017/04/16/Which-Fixtures-Should-Be-Connected-to-a-Grease-Interceptor

The Interceptor Whisperer latest article discusses internal vs external vented flow control. Read more here >>

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One benefit of our units being third-party certified (by NSF to ASME A112.14.3) is we know exactly how much grease our units will hold. The concrete gravity type vault doesn't have this benefit as there is no perfomance testing required and leaves inspectors to apply a general rule as to when the unit is full and in need of being pumped out. Schier's  GPSM (grease production sizing method) allows us to fine-tune the sizing based on food type and pumpout interval. If you had a similar size Subway and BBQ restaurant just counting DFUs and seats would basically size them out as the same size interceptor when they would be creating two completely different amounts of grease.

Well, good news. ASPE has adopted the GPSM into the latest handbook. Using this method reduces unnecessary expenses for your client while allowing you to specify a grease interceptor that will meet their needs and function properly.

​Read more here:
http://schierproducts.com/blogs/news/aspe-adopts-the-grease-production-sizing-method