Three-Compartment Sink Won't Drain: Clearing a Restaurant Warewash Line

A three-compartment sink is how a kitchen washes, rinses and sanitizes pots, pans and utensils by hand. When it stops draining, dishes stack up and so does the pressure. A compartment fills slowly, a drain gurgles, or water comes up in the floor sink beside it.

There is a plumbing reason the symptoms look different from a home sink. Maricopa County's guide calls for warewashing sinks to drain indirectly, with at least a one-inch air gap into a trapped receptor such as a floor sink. So a slow sink can mean the sink's own trap is clogged, or that the floor sink and the line beyond it are backed up.

We start by finding out which of those it is. If only one compartment is slow, the problem is local to that outlet. If all three drain slowly, or the floor sink fills when you empty the sink, the stoppage is downstream of the receptor.

The tech opens up the trap and drain connection to see what is in the line, then cables the line from the floor sink. Often the cable brings back grease and food solids, which tells us what the line is carrying. When the line is open and flowing, we run water to confirm it drains clean before we leave.

A cable gets the sink working that visit. If the stoppage keeps coming back or the cable meets something solid, we camera the line to see why. A coated line is jetted. A damaged or sagging line gets a proposal. A recurring problem usually has a root cause upstream, such as grease reaching the line because the interceptor is not keeping up, so we say so when that is what we see.

Stop using the sink and do not pour hot water or degreaser down it. Move warewashing to another approved station while it is out, and if the floor sink overflowed, treat it as a sewage backup. Our sewage backup reopening checklist explains what to clean and sanitize before you restart service.

Chain and managed sites often require a vendor check-in, a PIN or a work order number, and the manager on duty checks us in on arrival. Tell us at dispatch so the visit does not stall at the door. If the line needs a proposal, approval flows through whoever the work order names.