Short definition
A kitchen sink is the food-prep and wash-up fixture in a kitchen. Code defines it as a sanitary fixture with a 1½-inch trap, hot and cold supply, and a drain to the building’s sanitary system, terminating in either a basket strainer or a garbage disposal. It’s the most-replaced fixture in a typical home and the most common source of cabinet leaks and drain clogs.
What it is
Kitchen sinks come in single, double, and (rarely) triple bowls; in drop-in, undermount, integral, and apron-front mounts; and in five common materials — stainless steel, cast iron with porcelain enamel, enameled steel, fireclay, and granite or quartz composite. A typical residential bowl runs 7 to 10 inches deep; “deep” bowls go 9 to 10 inches; utility-style bowls go to 12.
Plumbing connections are standardized. The trap is 1½ inches under the Uniform Plumbing Code (which Washington adopts), the drainage fixture unit (DFU) load is 2 for a kitchen sink with a disposer, and the rough-in puts the drain stub at roughly 16 inches above the floor with cold and hot supplies at 18 to 20 inches. The faucet usually mounts on the back deck of the sink with 8-inch widespread or 4-inch centerset spacing.
The sink is also the highest-DFU drain fixture in most homes. Combined with grease — the number-one residential clog source — that makes the kitchen sink the place where drainage problems show up first.
Why it matters to a homeowner
Most homeowners replace or hire out a kitchen-sink swap at least once. Three practical anchors:
Failures happen here first. Cabinet floors warp from chronic sink leaks (basket strainer, P-trap, supply lines). Slow drains start here. Garbage disposal jams happen here. If you’re learning home plumbing, this fixture is the textbook.
Mount style is the buying decision. Drop-in vs. undermount drives counter material, install cost, and resale appeal. Single vs. double bowl drives daily ergonomics. Material drives durability and price. None of those affect the plumbing rough-in.
The connections are universal. A 1½-inch trap and a 1½-inch tailpiece on the bottom of either a basket strainer or a disposer means almost any kitchen sink swaps onto almost any kitchen sink rough-in. The cabinet may need adjusting; the plumbing rarely does.
Common variants and what a kitchen sink is not
- Kitchen sink vs. lavatory. A kitchen sink uses a 1½-inch trap; a lavatory (bathroom) uses 1¼-inch. The trap fittings are not interchangeable.
- Kitchen sink vs. utility/laundry sink. A laundry sink is deeper, often plastic, with a lower drain rough-in. Same trap size as a kitchen sink.
- Kitchen sink vs. bar/prep sink. A prep sink is a smaller second bowl on an island or perimeter run. Same trap size, smaller bowl.
- Single vs. double vs. triple bowl. Triple-bowl kitchen sinks are uncommon residential; double bowl is the norm; single bowl is gaining ground in modern kitchens (one large basin holds a sheet pan flat).
- Apron-front (farmhouse). A style where the front face of the bowl extends past the counter edge. The mount mechanics are still drop-in or undermount underneath.
Common failure modes
- Faucet drip — see the faucet entries.
- Basket-strainer leak under the sink — most common cabinet-floor cause.
- P-trap clog or leak — slow drain or weep.
- Disposer humming, leaking, or stuck — the most-Googled kitchen issue.
- Sprayer or pull-down spout hose leak.
- Cabinet floor warping from any chronic minor leak — fix the leak first, then evaluate the cabinet.