The restaurant that I manage has a consistent sink problem. We have a 3 bay sink, where all three bays have drains that connect to a single horizontal pipe, which then feeds into a small grease trap. Frequently when the one bay of the sink gets very full of water, or if all three bays get full, the sink will no longer drain, and dirty water backs up into all three sinks. The only solution is to use a plunger in the bay closest to the grease trap, plunge hard and then leave the plunger in place blocking that drain until the other sinks are empty. It still happens right after the grease trap is emptied, so I don't think that is related. Any ideas?

If it were related to the grease interceptor, it would overflow the cover when the sinks were backed up. IF it was installed properly, there is a "flow control" between the sink and the grease interceptor. If so, it has a "dinky" hole in the restrictor plate and something may be lodged in it. Or material could have accumulated in front of the plate. Also, do you remove the baffles in the trap when cleaning it?

Sure HJ.they cannot keep lunch down when the id is removed and you think they scraped the baffles!LOL.

Have the trap and the drain cleaned by a pro.

It sounds like your sink is hard piped all the way to the grease trap. I know our code here is that you have to have an air gap, where the sinks are indirectly tied to the drain on the floor. Maybe the vent pipe has been blocked by grease or something else, not allowing the air to escape when drained.

Actually yours sounds like a typical problem in the food service business. Especially if your horizontal waste pipe is piped directly into the interceptor. Your 3 bay sink should have lever handle waste dumps and 1-1/2 to 2 inch lines into the 3 inch horizontal. What type of material are your waste lines made of? PVC or Tubular brass.. or iron pipe. Food service restaurants using a lot of oil and grease should have their traps and interceptors serviced monthly, from the waste dumps and to the interceptor. If not, or enzyemes are being employed, some grease many have entered into the waste line, pass the interceptor. This will require more involvement with a licensed plumber.

Best Wishes

Many small grease trap installations I have seen have 2 clamps so the entire grease trap can be removed outside and cleaned out very well with a hose. This allows the majority of the mess to "NOT" be made in the kitchen area. Sometimes there will be a piece of pipe installed temporarly to replace the frease trap.

Like "WheelChair" stated there very well may be a stoppage on the down stream side of the grease trap.

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................ Good Luck .................

I like hj's answer but I don't know what a "dinky hole" is.

Here, they are usually hard piped, EXCEPT if the sink is for food preparation, then it has to be individually piped to a floor sink with an air gap. BUT, they ALL need the flow control ahead of the interceptor, and ALL flow controls have a small opening which will trap larger objects or scrubbing pads.

Our code wants Air Gaps for ALL sinks in commercial kitchens for this very reason. Hire a Pro before someone gets sick.

A "dinky" hole is littler than a "small" one. I have seen 3" flow controls with a 1" opening inside.

HJ I have serviced a few with baffled sheets with 1/4 holes .like a 12 x14" plate at the inlet.I love when I ask the kitchen manager if I open a door or two for air ,if it will be a problem.Did division of blind services here for a while.we started doing it after hours.To give the kitchen and dining area time to air out.LOL!Only smell that is worse is a raw fish bar floor drain after being backed up a week or so.

I have not smelled your fish, but I was in a Mexican carniceros (meat market). The fresh blood was dumped down the same sink that lead to the grease trap. Even with the doors open and exhaust fan on, it was powerfull when the weekly grease trap cleaning was done. He told me the first time he cleaned the grease trap was when the shop was open. The place emptied in seconds!

Hey all, since everyone on this post is talking about a 3 compartment sink issue. I was wondering if I could get some advice? I am in Florida and have a standard 3 compartment sink in a restaurant that has been direct plumbed forever and has passed inspections all along and runs directly into a small grease trap then runs outside and drops into a septic system. However, dept. of Ag has come along and said we now need to plumb with an air gap or air break to meet their code. We tried doing this per instructions from Dept. of Ag and did not work! Grease trap doing its job does not allow water to flow through and causes backup to come up the air gap. No one seems to know how to resolve this and still meet their code requirements? Any Ideas? FYI a Studor vent or high loop are not acceptable forms according to Dept. of Ag?
Help.
Bobby