Grease interceptors, floor sinks and three-compartment sink drains, from real restaurant and kitchen calls in Snohomish County
A restaurant kitchen keeps draining when three things hold up: the grease interceptor is installed with proper connections and its flow control, the floor sinks and their traps are supported so the pipe cannot drop, and the sink drains have cleanouts so a clog can be cleared without taking the line apart. Most emergency calls we get from kitchens trace back to one of those three.
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1. A grease interceptor that was glued in place
In October 2026 a restaurant on the Mukilteo Speedway called about a leak. Chase and Willie found three problems under the kitchen. A floor sink's three-inch band had come loose and let the pipe drop, so they replaced the band and added strapping to hold up the P-trap, because water falling into the trap was what loosened the band. A two-inch wye nearby had a joint with no glue in it, so they pulled it apart, cleaned it and glued it.
The third problem was the grease interceptor. Whoever installed it had glued the inlet and outlet pipes into the interceptor's fittings instead of using the proper connections, and those joints had worked loose. While Chase and Willie were working on it, both sides came off. They reconnected it temporarily with mission couplings, so no pipe had to be cut for the replacement, and tested every connection by running the dishwasher through four cycles and the prep sink at full flow for five minutes.
The kitchen was in service, so the full repair waited for a morning before opening. Later in October Logan and Willie installed a new interceptor to the manufacturer's specifications, reworking the inlet and the vent to fit its flow control fitting, then filled it until it was discharging from the outlet to test every joint.
2. Floor sinks behind the bar
A bar's floor sinks take glass-washer and ice-bin water all night, and they often share a small line. At a bar in downtown Everett in January 2026, nobody was on site when Connor and Logan arrived, so they tested every floor sink and the mop sink with water first. The mop sink and the back-of-house floor sink drained fine. The two floor sinks behind the bar did not. They share a two-inch line into the three-inch main, so the crew snaked the left sink, the shorter run, and cleared both. Then they ran both glass sinks while dumping a five-gallon bucket into each floor sink at once, to be sure the line could take a rush.
3. A three-compartment sink drain with no cleanout
Three-compartment sinks take the heaviest grease load in most kitchens. At a care facility's kitchen in Harbour Pointe, the dish-pit sink's lever waste valve was failing in July 2026. Chase and Willie replaced the valve and rebuilt part of the ABS below, adding a wye with a cleanout on the back side of the sink and a no-hub band so the drain can be taken apart without cutting. When something struck that drain about five weeks later and cracked the line to the floor drain, they cut out the broken section, rebuilt it with two couplings and a long-turn ninety, reset the waste valve, and dumped each compartment five times to check for leaks.
4. Know what is under your kitchen
The Speedway restaurant's old interceptor was a certified unit about sixteen inches wide, twenty-three inches long and sixteen inches deep, with four-inch openings fed by three-inch ABS. Knowing that, and where the floor sinks and cleanouts are, is what let us order the replacement and schedule the work around service. Keep a note of your interceptor's make and size with your maintenance records.
5. Schedule around service
You cannot take apart a grease interceptor while the dishwasher is running. When a repair needs the kitchen down, we diagnose and make it safe during the call, then come back before opening, as we did on the Speedway.
Restaurant Grease Drain Questions
Why does a restaurant grease interceptor leak at the inlet?
Most often because the pipe was connected the wrong way. On the Mukilteo Speedway in 2026, the previous installer had glued the inlet and outlet pipes straight into the interceptor instead of using proper connections, and the joints worked loose until both came apart. A leak at the inlet is a connection problem that pumping will not fix.
What is the flow control fitting on a grease interceptor for?
It limits how fast water can enter the interceptor, so a full sink dump does not push grease through before it has time to separate. It sits on the inlet side and needs its own vent, which is why Logan and Willie reworked both the inlet and the venting when they set the new Speedway interceptor in October 2026.
Why should a three-compartment sink drain have a cleanout?
Because that drain carries most of a kitchen's grease, and without a cleanout the only way in is to take the drain apart. When Chase and Willie rebuilt a care facility's sink drain in Harbour Pointe in 2026, they added a wye with a cleanout behind the sink and a no-hub band, so the next clog clears quickly.
Two floor sinks behind our bar back up together. Is that one clog?
Usually, yes. Floor sinks behind a bar often share one small line before they reach the main, so a single clog backs up both. At a downtown Everett bar in 2026, the two bar floor sinks shared a two-inch line, and clearing the shorter run from one sink opened both.
Our recommendation
Treat the grease interceptor as part of the plumbing, not just a box to pump. Have it installed with real connections and a vented flow control, keep its size and make on file, strap your floor sink traps, and put a cleanout on every three-compartment sink drain. Pumping on schedule matters too: Everett's own guidance is on our Everett commercial plumbing page. But a kitchen that is pumped on time can still flood if the interceptor's joints are failing.
Call a commercially licensed plumber
Stollwerck Plumbing & Sewer is commercially licensed and insured above Washington state requirements, and works on restaurant and commercial kitchen plumbing across Everett, Mukilteo, Lynnwood and Whidbey Island. Call and tell us what is backing up or leaking, and when your kitchen is closed.
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Related: commercial plumbing · commercial plumbing in Everett · commercial plumbing in Mukilteo · commercial plumbing in Lynnwood · commercial water heater replacement