Under Sink Grease Trap Service

Point of use is the whole idea

An under-sink unit is not a small interceptor. It is a different strategy. An interceptor waits outside and catches grease after it has traveled the building’s drain line, cooled, and had a chance to stick to the inside of every pipe on the way. A point-of-use trap catches it at the fixture, a few feet from where it came off the pan, while it is still hot and still moving. That is the argument for the small unit and it is a good one, because the grease that never enters your building drain line is grease that never has to be jetted out of it later. The tradeoff is that it only protects the fixture it is plumbed to. A trap under the three compartment sink does nothing for the wok station across the kitchen or the floor drain by the fryer, and a lot of kitchens discover this after a remodel moved the cooking and left the plumbing where it was. When we walk a small kitchen the first thing worth establishing is not the condition of the trap. It is which fixtures actually run through it, because that determines whether the unit is protecting the kitchen or protecting one sink while everything else drains straight to the lateral.

The most commonly mis-specified piece of equipment in a kitchen

Undersized point-of-use traps are everywhere, and the reason is structural rather than careless. The unit gets specified once, at build-out, against the fixtures on the plan and a rated flow the designer worked out on paper. Then the kitchen opens and reality diverges. A second sink gets tied in. A dish machine gets added or replaced with a faster one that discharges a large volume in a short burst. The menu changes, a fryer program appears, prep volume triples. None of those changes prompt anybody to revisit a beige box under a sink. The failure mode is specific and worth recognizing, because it does not look like a full trap. An undersized unit is overwhelmed by flow rate, not by accumulation. Water moves through it faster than the retention time the unit was built around, so grease never gets the seconds it needs to rise, and it exits with the water while the trap sits half empty and looks perfectly healthy. The tells are a kitchen with a small trap that never seems to fill but has a lateral that keeps needing attention, grease showing up downstream of a unit that was serviced last month, and a dish machine dumping into a unit rated for a hand sink. The fix is not a shorter interval. A shorter interval does nothing about flow rate. The fix is the right size unit, or a flow control device that meters the discharge so the trap gets the retention time it was designed for.

Small units, tight spaces and the practical realities

The unit is under a sink in a working kitchen, which shapes everything about the visit. Clearance is measured in inches. There is usually a disposal, a p-trap, a water filter and a shelf of chemicals sharing the cabinet. The floor is finished and the kitchen has to open in the morning. So the work runs tight and clean: the area gets covered, the hose run gets planned before anything is opened, and the unit gets emptied rather than dragged out into the room. Odor is the reason kitchens notice these units at all, and odor almost always comes from the same two places, which are the solids left on the floor of the unit by a partial service and a cover gasket that no longer seals. Both are cheap to get right and both are routinely missed. The hardware inside is small enough that it fails quietly: a strainer basket somebody threw away because it was inconvenient, a baffle that corroded off its mount, a flow diffuser knocked loose. Any of those turn the unit into a small holding box that passes grease straight through, and none of them are visible unless somebody actually looks while it is empty.

What goes into it upstream decides how often we come

On a unit this small, kitchen habits move the interval more than anything else. A sink strainer that is actually used keeps food solids out of the trap and can meaningfully extend the time between services. Scraping pans into the trash rather than rinsing them into the drain does more for a small trap than any product on the market. Hot water and detergent are worth understanding properly, because a heavy hot rinse emulsifies grease and pushes it through the unit still suspended in the water, and it then cools and drops out somewhere further down the line where you have no access to it. That is the actual mechanism behind a kitchen that religiously services a clean-looking trap and still has a lateral that blocks every spring. Enzyme and bacteria products sold for traps deserve a plain answer too. They do not remove grease from your building. At best they break it up, and broken up grease is grease that leaves the trap and reassembles in the collection system, which is why a lot of jurisdictions in this state prohibit them outright. There is no product that empties a trap. A truck empties a trap. Call 305-761-4311 and we will get a truck out for the unit you have.

Worth knowing

If your under-sink unit never seems to fill up but the line downstream keeps giving you trouble, stop assuming the trap is fine. That pattern is the signature of a unit undersized for the flow hitting it, and no service interval fixes a flow rate problem.