How to Install a Bathroom Sink

Here we offer general instructions and precautions for roughing in, as well as installation procedures for tying into your present drain waste vent and supply systems. When all the roughing in has been completed and you are ready to assemble your bathroom sink, your rough plumbing should resemble that shown here.

Most Common Mistakes

  1. Violating or ignoring local code restrictions,
  2. Using pipes that are too small,
  3. Attaching copper to galvanized without using a brass or dielectric fitting between the two,
  4. Not using PTFE tape or pipe compound at threaded joints,
  5. Not leveling your fixtures when installing them,
  6. Not installing an air gap filling for fixtures,
  7. Cutting supply stub outs too short to install the shutoff valves onto after the finished wall is in place, or
  8. Not properly aligning tubing into fittings or stop valves. (Forcing the nut onto the compression ring at an angle when the tubing is at an angle will cause a leak.)
  9. When turning the water back on in your home, always run the outside hose valve or flush your toilets to bleed dirt and air from the lines. This debris can cause problems in your sink faucets and other plumbing trim.

Installing Your Bathroom Sink

Pipes required for roughing in the bathroom sink include hot and cold supply stubouts, shutoff valves, transition fittings, and possibly flexible tubing for above the shutoff valves. Air chambers may also be required.

If you are installing the bathroom sink in a back to back arrangement, little pipe is required. Since a sink rates low in fixture units, it should have little effect on the present drain's efficiency. Refer to the fixture unit chart in the Uniform Plumbing Code Book. This fixture can often be wet vented if it is within the critical distance. If not, it must be back vented in some areas.

Clearance from the side of a bathroom sink to a toilet tank or finished wall should be at least 4 inches while distance to a tub may be as little as two inches. There must also be a minimum of 21 inches from the front edge to a wall or fixture.

When cutting the capped supply lines to install your shut off valves, cut the 1/2" copper supply line at least 1 1/2 inches from the finished wall to allow for an escutcheon and shut off valve compression nut and ring.

1. Cut carefully and slowly so as not to compress the pipe with the cutter wheel or flatten the pipe. The compression ring and nut will only tighten on a round pipe.

2. Assemble the faucet according to the directions on the package.

3. Slip on the escutcheon, the coupling nut, the compression ring and the valve. Hold the valve outlet up and slide it over the compression ring.

4. Tighten down the coupling nut onto the valve using two crescent wrenches. It will usually squeak when it is properly seated.

5. Connect the trap to the drain body and the drain pipe.

6. When water pressure is restored, run water into the basin and check for any leaks.