Extending Supply Lines


In a typical kitchen, hot and cold supply lines emerge from the wall just below the sink, where they are connected to stop valves. Supply pipes should run inside walls rather than through cabinets to protect them from damage. Pipes under a sink are liable to get bumped; these steps show the most durable installation, using drop-ear elbows and galvanized nipples.

Half-inch rigid copper pipe is large enough for most kitchen installations.

These steps show separate stop valves for the hot and cold faucet lines, the dishwasher, and an icemaker. If you want to add a water filter, hot-water dispenser, or other appliance, you may need additional stop valves. Saddle tee valves, which simply tap into a pipe, are easy to install but are prone to clogging.

Prestart Checklist

Several hours to run copper supply lines through a floor or wall

Drill, level, combination square, propane torch, groove-joint pliers, tubing cutter or hacksaw, fiber shield, C-clamps

Cutting and joining copper pipe, running pipe through framing

Install the drain line and carefully plan the location of the supply lines; shut off the water before beginning work

Copper pipe and fittings, flux, solder, galvanized nipples, stop valves, nailing plates, shims

Step 1

Where possible, run pipes through the centers of studs. Use a level or other long straightedge to mark for straight runs from stud to stud, and use a combination square to mark for the center of studs. Drill 3/4-inch holes to accommodate 1/2-inch pipe.

Step 2

Shut off water and drain the lines you will tap into. Cut the existing pipes and install new tee fittings. If you must run around a pipe or other obstruction, use 45-degree elbows and street elbows.

Step 3

Usually, the most convenient location for stub outs is on each side of the drain trap adapter, as shown. But you can place them wherever they will be within easy reach, as long as they are within 18 inches of the faucet inlets. At each stub out, install a hammer arrester and a drop-ear elbow. Do a dry run (shown), then sweat the fittings and reattach the drop ears to the braces. Add nipples with caps; turn on the water and check for leaks.

Preparing the Cabinets

Once the drain and supply pipes have been installed and tested for leaks, run any electrical lines for receptacles and lights. Cover the walls with drywall and prime and paint. Install the finish flooring, then protect it with cardboard or heavy paper and a drop cloth.

Unpack the sink, garbage disposer, dishwasher, and any other appliances and check the manufacturer's literature for installation requirements. Pay particular attention to the dimensions of the opening for the dishwasher, as well as the size and location of the holes for its drain and supply lines.

A sink base cabinet has no drawers or shelves, providing room for all the appliances, tubes, and pipes that must fit inside it. Some sink bases are actually completed cabinets, while others consist of only the face and the floor.

Prestart Checklist

A day to install cabinets, plus several hours to run the wiring for the dishwasher

Hammer, drill, level, groove-joint pliers, adjustable wrench, tape measure, screwdriver, hole saw

Measuring, drilling, and sawing accurately to install cabinets that are level and properly spaced

Run and test all the rough plumbing

Cabinets, shims, screws, tees, nipples, pipe-thread tape, stop valves, 14/2 armored cable

Preparing the Cabinets: Step 1

Shut off the water and drain the line. For each supply remove the cap from the nipple and slide on a flange to cover the hole at the wall. Wrap the nipple threads with pipe-thread tape and install a tee. Wrap Teflon tape around the threads of two short nipples and screw them into the tee fitting. Screw stop valves onto the nipples. Turn the valve handles off and restore water pressure to test for leaks.

Preparing the Cabinets: Step 2

The dishwasher opening should be 24-1/4 inches wide for most models; check manufacturer's instructions. If installing a cabinet on the other side of the dishwasher, as shown here, level it from the sink base cabinet, plumb, and fasten it in place.

Preparing the Cabinets: Step 3

Run an electrical line for the dishwasher. Usually a 14/2 armored cable connected to a 15-amp circuit is sufficient, but check codes and the manufacturer's literature. Be certain that the dishwasher will not overload the circuit. Hire an electrician if you are not sure of your wiring abilities.

Preparing the Cabinets: Step 4

The dishwasher instructions will tell you the best place to drill a hole for running the drain and supply lines. Usually a single 1-1/2-inch hole is sufficient.

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