Kitchen Sinks, Faucets and Plumbing: What to Decide Early

The sink is the most used spot in the kitchen, and almost every choice around it has to be made before cabinets are ordered or pipes are roughed in. This page covers those choices in the order they come up, with the plumbing code points that affect them. Code references are to the 2021 Uniform Plumbing Code (UPC) as adopted in Washington, in force since 15 March 2024 and current as of October 2026.

Sink configuration and mounting

Decide three things: how many bowls, how the sink meets the counter, and how wide it is.

• Single bowl. One large basin fits sheet pans and stockpots flat.
• Double bowl. Two basins let you wash and rinse, or keep a disposal side separate. Each bowl is smaller. An offset or low-divide version is a middle path.
• Workstation sink. A single bowl with ledges that carry a cutting board, colander and drying rack.

For mounting, an undermount sink hangs below a solid countertop so crumbs wipe straight in. It needs stone, quartz or solid surface. A drop-in sink has a rim that sits on the counter and works with any material, including laminate. An apron-front (farmhouse) sink replaces part of the cabinet face and needs a cabinet built for it.

The sink's width sets the sink base cabinet, and the model sets the countertop cutout. Have the actual sink chosen, and ideally on site, before the fabricator templates. See kitchen cabinets and countertops for how those orders are sequenced.

Sink materials compared

Faucets and extras

Pick the faucet with the sink, because the number of holes drilled in the sink or countertop has to match. A pull-down sprayer with a single lever handle is the workhorse. Bridge and two-handle faucets suit traditional kitchens but need more holes. Touch and touchless models need power under the sink, from batteries or a receptacle.

Count everything that needs a hole or a place under the sink: faucet, soap dispenser, air gap, filtered water tap, disposal switch.

• Pot fillers need a supply line in the wall behind the range, decided before rough-in.
• Filtered or instant hot water needs cabinet space for the filter or tank, and a tank needs a receptacle.
• Refrigerator ice makers need their own supply line and shutoff.

The UPC requires a control valve immediately ahead of each water-supplied appliance and each appliance supply (UPC 606.5). In plain terms, every one of those extras gets its own shutoff. Where static water pressure is above 80 psi, the code also requires a pressure regulator to bring it to 80 psi or less (UPC 608.2).

Disposals

A food waste disposer takes space in the sink base, needs a switch and a receptacle, and changes the drain layout. Under UPC 419.2 the waste line receiving a disposer's discharge must use an approved wye or other directional fitting, and no dishwasher drain may connect to the tailpiece, continuous waste or trap on the discharge side of the disposer. The disposer also needs a cold water supply (UPC 419.3), which the faucet provides in a normal installation.

On the electrical side, the 2023 National Electrical Code requires ground-fault protection for receptacles in a dwelling kitchen, and that now includes the one under the sink for the disposal. The kitchen electrical code page explains what a remodel triggers.

Dishwashers and the air gap rule

Washington follows the UPC on this, and the UPC is strict. Section 807.3 says no domestic dishwasher may be connected to the drainage system or a disposer "without the use of an approved dishwasher air gap fitting on the discharge side of the dishwashing machine." The fitting's flood-level marking must sit at or above the flood level of the sink or drainboard, whichever is higher. From the air gap, the dishwasher may discharge into a wye fitting on the sink tailpiece or the dishwasher inlet of a disposer (UPC 414.3).

The air gap is the small capped fitting on the counter or sink deck beside the faucet. It needs its own hole, so tell the fabricator.

For placement, the National Kitchen & Bath Association suggests the nearest edge of the dishwasher sit within 36 inches of the nearest edge of the sink, with at least 21 inches of standing room between the dishwasher and any counter, cabinet or appliance at a right angle to it. Those are planning guidelines, not code.

Moving the sink

Keeping the sink where it is saves money. Moving it is often worth it anyway, but understand what moves with it:

• The drain must slope at 1/4 inch per foot back to the stack, which limits how far a sink can travel before the pipe runs out of floor depth.
• The vent. Every trap needs a vent within a set distance (UPC 1002.2). S-traps and unvented traps are prohibited (UPC 1004.1), and the tailpiece between sink and trap may not exceed 24 inches (UPC 1001.2).
• Supply lines, hot and cold, plus any filter, ice maker or pot filler lines.
• Whatever the pipes pass through. Over a crawl space the work is done from below. On a concrete slab the floor has to be cut and patched. In a two-story house the ceiling below may open.

What drives the cost is distance from the existing drain and vent, the floor construction, and how much finished surface has to be opened and repaired. JDI does not publish a separate price for moving a sink, so ask for it as its own line in your estimate.

Moving a sink needs a plumbing permit in the City of Vancouver. The city's exemption covers removing and reinstalling a sink only where the work does not "involve or require the replacement or rearrangement of valves, pipes or fixtures" (VMC 17.08.090(D)(3)). As part of a remodel, plumbing is included in the residential building permit. The plumbing permit guide covers the county and nearby cities.

Venting an island sink

An island has no wall to carry a vent up to the roof, so the UPC provides a specific method, the island loop vent (UPC 909.1). The vent rises from the trap as high as possible inside the cabinet, not less than the drainboard height, then loops back down and connects to the horizontal drain. A foot vent is taken off below the floor, run to the nearest partition and continued up through the roof or tied into other vents. The loop takes up room in the sink base that you might have planned for a pull-out, so account for it.

Air admittance valves, the one-way mechanical vents sold as a shortcut, do not appear in the body of the 2021 UPC and Washington's amendments do not add them. Whether the City of Vancouver will approve one as an alternate method was not confirmed. Ask the plans examiner before designing around one. For the rest of the island decision, see kitchen islands.

What to settle before rough-in

1. Sink model, bowl layout and mounting style.
2. Faucet and every accessory that needs a hole, a shutoff or power.
3. Sink location, and whether the drain and vent can reach it.
4. Disposal or no disposal, and where the switch goes.
5. Dishwasher side and air gap position.

JDI Construction designs and builds as one team, so the plumbing route is checked against the cabinet plan before anything is ordered, and we handle the permits. The Washington code is due to change: the State Building Code Council's schedule sets final adoption of the 2024 plumbing code for 16 October 2026 with an effective date of 3 May 2027, so confirm these rules again if your permit will be issued after that. To talk through your own kitchen, start with kitchen remodeling in Vancouver or check whether your project needs a permit.