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Semi-automatic draw-off; a failed concept

Years ago, someone thought they had discovered the perfect solution for grease interceptors installed indoors. Most industry professionals are fully aware of the problems associated with indoor installations relating to maintenance. The only way to clean them out is it remove the cover. That exposes the kitchen, and hence the rest of the facility, to noxious odors.


So, along comes something different. A new design that "promises" to prevent the noxious odors inside a grease interceptor from entering the atmosphere inside the kitchen area.


The problem with the proposed solution is that it doesn't do what it promises to do. In fact it CANNOT do what it promises to do. Let me explain first how the device works in theory:


When you are ready to clean the grease interceptor, you run the sinks that connect to the grease interceptor with hot water, preferably at least 140 degrees (F) for at least two minutes. This is supposed to heat up and liquefy the collected fats, oils and grease (FOG). Then you close the valve on the outlet, preventing any of the contents from discharging downstream, and you open the valve on the top of the unit where the discharge hose or pipe is located. Next you run the sinks with hot water again for three to five minutes to fill the grease interceptor up with water. The FOG floats on the top of the wastewater inside the grease interceptor and as you fill the device up with water it is supposed to force the FOG up inside a cone where it is supposed to be forced through the hose or pipe outside the interceptor where it can be collected.


There are at least three problems with the design and application of the semi-automatic draw-off:


1. What is the discharge hose or pipe connected to?

If the discharge hose or pipe is not connected to a container located outside the kitchen area then the user must bring a container over to the grease interceptor to collect the contents that are discharged during the cleaning process.


If the point of the device is to prevent noxious odors from entering the atmosphere in the kitchen area, then discharging the contents of the grease interceptor into a container that is OPEN to the kitchen area defeats the purpose. The contents and noxious odors are exposed to the kitchen area from the open container where they have been collected.

2. What about solids?

Food debris is a always present in grease interceptors. It is not possible to prevent all food debris from entering a grease interceptor no matter how diligent a kitchen staff is. Food solids are typically heavier than water and settle out on the bottom of grease interceptors. When cleaning a grease interceptor, food solids must be removed to ensure the device continues to operate correctly. Because these solids are heavier than water, they CANNOT be pushed out the top through the discharge hose or pipe.


The ONLY way to remove collected solids is to OPEN the grease interceptor and physically remove them. This must be done EACH time the grease interceptor is cleaned. If the purpose of the semi-automatic design is to eliminate the need to open the cover of the grease interceptor for maintenance purposes, you can see that having to remove the solids makes that impossible.


3. Who is doing the maintenance?

Most liquid waste haulers will admit that they do NOT follow the procedure outlined by manufacturers for cleaning a semi-automatic grease interceptor. Instead, they open the cover and stick their pump out hose inside the device and evacuate the contents the way they do for any type of grease interceptor.


While proponents of these devices might fantasize that the manufacturers cleaning instructions will be followed, the reality is that pumping contractors are not paid by the hour, they are paid by the job. The faster they get the job done the more jobs they can do. The fastest way to clean out any type of grease interceptor is to pump out the contents through the cover. The fact that they have to open the device to clean out the collected solids as well, dictates that the most efficient method of cleaning these tanks is to open the cover and pump out all of the contents and SKIP the manufacturers instructions.


If you truly want to prevent noxious odors from entering the atmosphere in a kitchen area, there is a better solution: A remote pump out port.


Images courtesy of Schier Products

The advantage of this strategy is that the internal piping goes all the way to the bottom of the grease interceptor where it can remove all of the collected FOG and food solids. While the remote pump out port is under vacuum, you can remove the cover and you will not smell ANYTHING. That means that the contractor can spray down the interior of the tank and give it a thorough cleaning and there will be NO noxious odors entering the kitchen area during maintenance.


Semi-automatic grease interceptors fail to deliver on the "promise" that you won't have to open up the grease interceptor to maintain it. In fact, to correctly clean out a grease interceptor you MUST open the cover to remove ALL of the contents.


A remote pump out port ACTUALLY allows for a thorough cleaning, while doing a much better job of preventing noxious odors from entering a kitchen during maintenance operations.



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