Kitchen Remodel Plumbing

What plumbing changes in a kitchen remodel?

Kitchen remodel plumbing changes whatever moves: the sink drain and its vent, the hot and cold supplies, the dishwasher drain and supply, the refrigerator water line and, in many kitchens, a gas line to the range. If the sink stays put and only the faucet and sink change, the plumbing work may be small.

The permit line falls at concealed or moved pipe. The model codes exempt very little (leak repair, clearing clogs, resetting a toilet with nothing replaced), and your city's list decides the rest. The City of Bend, Oregon, for example, requires a plumbing permit to alter piping inside a wall, ceiling or beneath a floor. The plumbing permit page covers how to check your own city's list.

Once the pipes are in, the 2021 IPC sets a rough-in inspection before wall or ceiling coverings go on. Cabinets and drywall wait until it passes.

Can you move a kitchen sink?

Yes, a kitchen sink can usually move, but the new drain has to reach a branch or stack with enough slope, and the trap has to stay within reach of a vent. That second limit is what decides how far the sink can go along a wall without a new vent.

Under the 2021 IPC, 1/4 inch per foot is the minimum slope for drains 2-1/2 inches and smaller, which covers most kitchen sink drains. The same code's Table 909.1 lets a 1-1/2 inch trap sit up to 6 feet from its vent and a 2-inch trap up to 8 feet, both at 1/4 inch per foot. Your local code may differ, so the plumber designs the run and the inspector approves it.

Moving a sink on a wood floor means drilling joists or running pipe below; on a slab it means cutting concrete. The page on moving a toilet or shower drain explains the slab side, and the plumbing vents page covers how vents work.

How is an island sink vented?

An island sink has no wall behind it for a normal vent, so it is vented by a method your local code accepts: an island fixture vent run under the counter, or an air admittance valve where allowed. The plumber chooses the method and the inspector approves it.

The ICC's article on the 2021 IPC describes island fixture venting as a method limited to sinks and lavatories, where the vent rises above the fixture's drain outlet before turning, and cleanouts let the vent piping be rodded. It also says residential kitchen sinks with a dishwasher or food waste grinder connection are allowed on it.

Air admittance valves (AAVs) are the other common answer. Oatey describes them as used where local codes permit, such as remodels with island sinks. Under the 2021 IPC, individual and branch AAVs meet ASSE 1051, stay accessible, sit at least 4 inches above the drain they vent, and the house still needs at least one vent to open air. In UPC jurisdictions they are generally not allowed unless the state or city has added them; Iowa's plumbing board, adopting the 2021 UPC, declined to allow them.

What do dishwashers and fridges need?

A dishwasher needs a hot supply with a shutoff, a drain hose with a high loop or an air gap, and a circuit from an electrician; a refrigerator with an ice maker needs a small water line with its own shutoff. Both are set at rough-in so the cabinets can be built around them.

• Dishwasher drain. Bosch's instructions say the hose must have a high loop or an air gap, with part of it at least 33 inches off the floor on that model, and an air gap installed if a local ordinance requires one. Some cities do: the City of San Bruno, California requires an approved air gap above the sink's flood rim.
• Disposal connection. Bosch notes the knockout plug in the disposal's dishwasher inlet has to be removed before the hose goes on.
• Hose length. That Bosch model allows up to 150 inches of drain hose, including the run to the air gap.
• Refrigerator line. KitchenAid's refrigerator help page calls for 1/4-inch OD soft copper or PEX with a coil left as a service loop, and warns against piercing-type or 3/16-inch saddle valves.

Who runs gas for a range?

A licensed plumber or gas fitter runs or extends gas piping for a range; this site gives no steps for gas work. State law often treats gas piping as plumbing: Texas includes piping that supplies gas in its legal definition of plumbing, and California's C-36 plumbing classification covers gas piping from the meter.

Rules for homeowners vary by state; Texas, for example, has a homestead owner exemption. The safe default is that gas work usually requires a licensed plumber or gas fitter, so check your state and local rules, and ask the building department what permit and inspection new gas pipe needs in your city.

In what order does kitchen plumbing happen?

Kitchen plumbing happens in two visits around the cabinets: rough-in after demolition and framing, then trim after the counters are set. In between come the rough inspection, wallboard, cabinets and countertops.

1. Demolition and layout. Mark the sink, dishwasher, fridge and range locations from the cabinet drawings.
2. Rough-in. Drain, vent and supply lines are run and capped; gas is run by a licensed pro if the range moves.
3. Tests and rough inspection. Drain and vent tests and the inspection happen before the walls close. Photograph every open wall first.
4. Walls, cabinets and counters. The sink base and counter cutouts are built around the stubs.
5. Trim. Sink, faucet, disposal, dishwasher and fridge line are connected, and the final inspection follows.

The rough-in plumbing page and the trim-out stage explain the two visits in more detail. Choose the sink and faucet before rough-in. A supply house listing such as Plumbing Supply and More's kitchen sinks (Plumbing Supply and More, run by the owners of Trench to Trim) shows how sinks are specified (bowl depth, drain size, mounting), so the bid line makes sense; installation stays with the licensed plumber.

Kitchen numbers

• 1/4 in. per ftMinimum slope for drains 2-1/2 inches and smaller, 2021 IPC Table 704.1ICC
• 8 ftLongest 2-inch trap-to-vent distance at 1/4 in. per ft, 2021 IPC Table 909.1ICC
• 33 in.Height part of the dishwasher hose must reach on one Bosch modelBosch
• 4 in.Minimum height of a branch AAV above the drain it vents, 2021 IPC 918.4ICC

Questions from the job site

More remodel pages

• Stage folder: Remodel plumbing in the right order
• Remodels: Bathroom remodel order, step by step
• Trim-out: What gets done at plumbing trim-out