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Hot Water Turns a Trap Into a Pipe

This is the most common expensive mistake in a commercial kitchen and it is invisible from outside the device.

The short form

A grease trap separates grease by letting it cool, congeal and float. EPA puts dish machine discharge at 140 to 180 degrees Fahrenheit, with detergents and a high flow rate, and states that a pre-rinse sink may be connected to a trap but the dish machine may not.

Source: U.S. EPA, FOG Management and Control Program.

InterceptorCall is a referral service, not a contractor. We connect operators and property managers with independent contractors. Contractors and waste haulers are required to hold whatever credential and permit their state or municipality demands — ask to see them, because the manifest they leave you is a compliance record. We carry out no work, we haul nothing, we do not set prices, and we never charge the caller anything. Nothing here states the grease limit, the pumping interval or the device size that applies to any particular kitchen; those are set by your control authority and by your installation.

How a trap actually separates anything

By waiting. Grease arrives dispersed in hot water, the water slows down inside the vessel, the grease cools, congeals and rises, and the outlet draws from beneath it.

Every part of that depends on the water cooling. Remove that and the device still fills, still needs pumping and still looks exactly the same.

What a dish machine sends

EPA’s material puts dish machine discharge at 140 to 180 degrees Fahrenheit, along with detergents and a high flow rate, and states the rule plainly: a pre-rinse sink may be connected, but not the dish machine.

The same grease trap at sink temperature and at dish machine temperatureTwo identical traps drawn side by side. In the first, fed at ordinary sink temperature, grease has cooled and formed a layer held at the surface. In the second, fed at dish machine temperature, no layer has formed and the grease is shown passing through the body of the trap and out of the outlet.HELD HEREAT SINK TEMPERATUREgrease cools, congeals and floats,which is the entire trickstraight throughAT 140 TO 180 DEGREES Fgrease stays liquid and leaveswith the flow, unretained
A trap separates grease by letting it cool. Water hot enough to keep it liquid turns the same device into a length of pipe, and nothing about the outside of it looks any different.

Three separate attacks on the same mechanism. The heat keeps the grease liquid. The detergent emulsifies it so it will not separate even when it cools. The flow rate cuts the retention time the device needed in the first place.

Source: U.S. EPA, FOG Management and Control Program.

Why it is so often wrong

Because connecting it looks correct. The dish machine produces greasy water; the grease device handles greasy water; the pipe run is short. Nothing about the installation looks like a mistake, and the device does not complain.

It fails silently and the evidence turns up downstream, in somebody else’s sewer line, attributed to your address.

The other thing heat does

Federal law separately prohibits heat in quantities that push the treatment plant above 40 degrees Celsius, 104 Fahrenheit. That is a plant-wide threshold rather than a pipe-level one, but it tells you how the rules regard hot discharges in general.

Source: 40 CFR 403.5, National pretreatment standards: Prohibited discharges.

What to check

Where the dish machine drain actually goes, which is a question for whoever installed it and frequently nobody knows. Whether the trap is sized and rated for what is reaching it. And whether a flow restrictor is present and is the external type EPA’s material prefers.

If the answer is that the machine tees into the trap, that is a plumbing change rather than a cleaning problem, and it is worth saying so on the call so the right trade turns up.

Have the last manifest in front of you.Date, hauler, volume removed and where it went — it is the first thing anyone asks for and it tells a contractor more about the state of the vessel than a description does. We will route you to somebody who covers your area, identified from the ZIP code of the premises, and you are never charged. Other plumbing work at the premises can be arranged through the same call.

Call (888) 753-1770
Call (888) 753-1770