Basement Power/Water: Plumbing

Home | FAQ | Finishing | Sump Pumps | Foundations

For those who have basic skills in cutting and soldering copper pipe, the job of adding piping to supply water to a basement sink or toilet is straightforward. Providing a drain and vent for the water, however, remains a difficult job. The following information is meant to provide do-it-yourselfers with an idea of what is involved in such a project. This is a job, however, for a professional. Especially if the basement is below the level of the existing DWV (drain/waste/vent) system. (It usually is.) Contact a plumber before finalizing a room arrangement in the basement. He or she will probably suggest a placement or fixtures that minimize effort and expense.

Adding New Supply Lines. The hot and cold water supplied to fixtures throughout the house runs through copper or (in older houses) galvanized-steel pipes. New pipes are nearly always copper. The water in a household supply system is under pressure, so pipes can run at all angles. This makes it easy to supply the basement with water. After turning off the water at the main, draining the water to the lowest fixture, and tapping into an existing line, simply solder lengths of copper pipe together until the fixture is reached. The lines to each fixture terminate in a shutoff valve. When adding supply lines, run piping parallel with the floor joists wherever possible, and tuck it into the space between joists.

Relocating Existing Supply Lines

Pipes that supply water to fixtures upstairs are often attached to the underside of the floor joists. If a dry wall ceiling is to be installed in the basement, the pipes have to be relocated. This can be done if there are not many pipes to move. (However, if the house has hot-water or steam radiators, there will be too many pipes to move. Consider a suspended ceiling instead.) The existing pipes may be reused, or it may be easier to replace the old pipe with new pipe.

1. Marking the Runs. Run a carpenter’s pencil or a marker along the sides of the existing horizontal pipes to mark the underside of the joists for notches. The pipes most commonly encountered are ½ inch, ¾ inch or 1 inch. (These are internal measurements.) The outside of a copper water pipe is about % inch larger than its internal dimension, so notches range from about % inch wide to 1¼ inches wide.

2. Measuring for Cuts. Before removing the pipes, figure out how much they have to be raised. To minimize the depth of notches in the joists, the bottom of the pipes can sit flush with the bottom of the joists. Measure from the bottom of a pipe to the underside of a joist. Add A inch to this dimension to allow for pipe fittings. The total is the amount that needs to be cut off of each riser in order to raise the pipes.

3. Cutting the Risers. Use a pro pane torch to liquefy the solder in the existing fittings so that you can disconnect them. Then use a tubing cutter or, if space does not permit, a mini-cutter or a hacksaw to cut the risers. Remove a piece equal in mea sure to the distance that the pipes are to be raised. Then use a hand saw or saber saw to cut notches in the joists. Use the marks drawn in Step 1 as a guide.

4. Reconnecting Pipes. To promote a good solder joint, clean out the fittings on the existing pipe runs. Then lift the runs into place, and solder them together. A metal plate covers each notch to protect piping from possible nail punctures.


1 - Mark the location of the notch on the underside of each joist.


2 - Measure from the bottom of the pipe to the underside of a joist. Add 1/4 in. to get the cutoff distance.


3 - If possible, use a tubing cutter to cut each riser. Then prepare to re-solder the pipes and fittings.


4 - Fit the pipe runs into notches, and re-solder all of the fittings. Nail a metal plate over each notch to protect the pipe from nail punctures.

Top of Page Home Prev: Wiring in Masonry Walls Next: Basement Finishes

Updated: Wednesday, August 10, 2011 5:39