How To Replace A Bath Tub Faucet - Part 2 - Plumbing For A New Tub/Shower Valve

Bath Remodel:

Replacing A Bath Tub Faucet
Part 2 of 2
Installing A New Tub/Shower Valve

In This Article: We prepare some sections of pipe to screw into the tub valve, put the valve in place, and connect to the existing pipes. And we install the shower riser pipe.	Related Articles: Index of Bath Articles Index of Plumbing Articles Part 1 of Replacing A Bath Faucet Replacing A Tub Drain
Skill Level: 3-4 (Moderate +)	Time Taken: 5 Hours

By Bruce W. Maki, Editor

This is the second part of a two-part article. Click here to read the first part.

I made a collection of pipes with threaded adapters on one end.

A closer view of the 3/8" compression fitting adapter. Note how the threads are straight, not tapered.

Pre-assembling bath tub faucet before installing.

I installed the hot and cold water supply pipes into their respective ports in the faucet valve. I used a pair of adjustable wrenches to tighten both pipes simultaneously.

These fittings must be very tight to seal properly. My plumbing sources tell me that the official procedure is to first tighten the fitting by hand, and then use a wrench to turn the fitting 1 to 2 additional turns. Remember this: at least 1 turn, at most 2 turns, after hand tightening.

I installed the shower riser pipe (which was only about half as long the pipe needed to be) and the tub fill pipe into the faucet valve.

I also installed the "lookout" pipe into the spout. This pipe was intentionally made a little too long.

Tub faucet set in position before connecting pipes are cut.

I set the faucet in position (after I reinstalled the white plastic round plate on the valve).

Note how the lower tube was deliberately made a little too long. It is easier to cut a pipe shorter than make it longer.

I marked the length to cut the pipe.

I set the spout "lookout" pipe in place (red arrow).

This pipe was also made a little too long, and I marked where to cut it.

I soldered an elbow to the two pipes.

Warning: This was risky, because of the presence of wood right beside the fitting. Soldering around combustible materials requires a heat shield to prevent starting a fire.

Also, I keep some water nearby, such as a bucket and/or a spray bottle.

I soldered a piece of pipe to a drop-eared elbow, which is used to anchor a threaded shower head pipe.

I temporarily installed a 1/2" pipe nipple (short piece of threaded pipe) to the drop-eared elbow and stuck the assembly in the hole.

I also installed a piece of 2x4 blocking to support the drop-eared elbow.

When the real shower head tube is installed, the drop-eared elbow will have some solid backing behind it. Otherwise, it would be difficult or impossible to thread the shower tube into the elbow.

For the shower riser, I had two pipes that simply needed to be connected.

I used a short piece of pipe and two couplings to complete the shower riser.

The lower coupling has a "rolled stop" (notice the crease in the center). The upper coupling has no stop. This "non-stop" fitting is needed when there is no flexibility to move the pipes apart and slip them into the fittings.

Just to make sure the elbow did not move sideways, I secured it to the 2x4 block with some wire ties.

The temporary pipe is still holding the shower riser in place. I removed this pipe...

... and installed the shower head tube. I wrapped some Teflon tape around the threads and tightened it with a small pipe wrench.

I installed the face plate.

At this point I shut off the water to the old faucet. I try to work as far as I can before turning off the water.

I used a small tubing cutter to cut the supply lines.

I used a tubing bender to bend the 3/8" copper tubing into the desired position.

Bending Copper Tubing:

Trying to bend copper tubing without a proper bending tool is asking for trouble. It takes some skill to bend tubing by hand without kinking it. Once kinked, the tube can never be unkinked, and the kink will restrict or block the flow of water.

I have been able to bend tubing by using some sort of curved form to bend against. One of the best curved forms is a PVC pipe fitting, such as an elbow. I have used elbows from 1½" to 3" as a bending jig, and it works well.

This is a 3/8" "All Tube" Tee fitting. It can be used for copper and plastic tubing. The brass inserts are not needed for copper tubing.

On the hot water side, I made a short section of tubing to connect between the 3/8 adapter and the new tee that I installed.

This is a union fitting that I used to extend the cold water line.

The finished supply piping.

Working with tubing and compression fittings is easy, and there is no risk of burning down the house. But... extra care must be taken when bending tubing. If a kink develops, further flexing of the tubing will almost surely cause a leak.

Tub faucet plumbing where supply pipes are soft copper tubing.

Okay, you caught me! The tube that comes out of the tee fitting is the hot water supply... but it enters the faucet on the right side (when viewed from inside the tub) which is also the wrong side!. The old valve was plumbed backwards, so hot and cold were reversed.

The beauty of Moen's valve design is that it doesn't matter which side is connected to hot or cold. If the supplies are reversed, all you need to do is remove the faucet handle and use a pair of needle-nose pliers to rotate the cartridge 180 degrees, replace the handle, and the situation is fixed.

The finished tub-and-shower valve installation.

I later removed that hideous old tub faucet down below and covered the holes.

The tub spout stuck out from the wall a bit, so I placed some shims between the pipes and the wall to pull the pipes back.

Replacing A Bath Tub Faucet Part 2 of 2 Installing A New Tub/Shower Valve

This is the second part of a two-part article. Click here to read the first part.

Further Reading:

Replacing A Bath Tub Faucet
Part 2 of 2
Installing A New Tub/Shower Valve