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Kitchen Plumbing

by Don Vandervort, © HomeTips

Most kitchens have a fairly simple plumbing setup that includes hot- and cold-water supply lines, a waste line for the sink (or sinks), and, for kitchens with a gas range, a gas supply pipe.

kitchen plumbing diagram

Many kitchens also have hookups for dishwasher, disposer, icemaker, water treatment system, and/or instant hot water, but these are generally tied in to the sink’s plumbing.

Kitchen Sink Plumbing

The visible part of the sink’s plumbing is nearly always located directly below the sink, inside the sink’s base cabinet. There you can generally see two small shutoff valves: one for the hot water supply, the other for the cold. Turning these valves clockwise stops the flow of water through the flexible supply tubes that route water to the faucet.sink drains diagram

On the faucet side of the cold-water shutoff valve, there may be other water connections too—sometimes by way of a saddle valve. This is generally where connections are made with flexible copper or plastic tubing to serve a water treatment device, icemaker, or instant hot water dispenser.

A sink drains by way of several components. The strainer fits into a strainer body that’s inserted down through the sink hole and sealed with a bead of plumber’s putty.

Underneath are a rubber gasket and metal washer, and a large locknut or retainer tightens the body in place. A straight tailpiece mounts to the strainer body by means of a threaded coupling.

Slip joint couplings connect the tailpiece, the main parts of the trap, and a short threaded nipple at a tee in the drainpipe. At the wall or the back of the cabinet, a trim piece called an escutcheon hides the connector and the nipple. The sink trap, always filled with water, seals the pipe so sewer gases won’t enter the house. Waste water exits through the trap and down the vented drainpipe to the main stack.

A garbage disposer mounts directly to a special strainer body. The trap then connects to an outlet on the disposer. Kitchen sinks may have single or multiple bowls in a variety of shapes and sizes. They’re mounted in three different ways, depending on the type: self-rimming, flush, or under mounted. Self-rimming sinks have a molded edge that overhangs the countertop.

Flush sinks are supported by metal strips around the perimeter or are an integral part of the countertop material. Rimless or under-mount sinks are fastened or fused to the underside of the countertop.

Kitchen Gas Hookupskitchen gas hookups valve

A small, flexible supply line delivers the gas to the appliance. A gas range is generally served by a flexible gas connector, controlled by a gas valve located at the wall or floor beneath the cooktop or range.

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