Bath Remodel: Installing A Moen Posi-Temp Shower Faucet

By Bruce W. Maki, Editor

Installing a new shower faucet is less difficult than it seems, especially when done as part of a total bathroom remodeling project. Yet there are some important dimensions that must be strictly observed for the faucet to work right. The instructions mention some of these issues. For example, the valve must not protrude from the drywall at all, or the faucet's cover plate will not seal against the wall.

The height of the valve is another issue. I placed the center of the faucet at 48 inches above the floor.

Start At The Valve And Work Backwards:

After making some measurements, I connected three sections of 1/2" copper pipe to the valve body.

 

Each section of pipe has a male threaded adapter soldered to the end. The male threads were coated in pipe thread compound (sometimes called pipe "dope") before screwing together.

These connections require a pipe wrench to hold the valve body and a large adjustable wrench to turn the male threaded adapter. It's worth mentioning that I bought the wrong faucet here. I intended to pick up a faucet with solder connections. I would have returned it to the store, but I bought it in another part of the state, a 2-hour drive away.  I prefer to use a shower faucet with soldered connections because threaded connections are difficult to make water-tight, and a small drip concealed in a wall cavity can cause considerable damage.

 

Excess thread compound was wiped off, otherwise the goo gets everywhere. It takes a lot of torque to prevent these connections from leaking. One of the challenges for beginners is to become familiar with just how tight threaded connections must be. Connections that will be immediately hidden behind drywall are not good places to practice.

This Moen Posi-Temp shower valve is exactly the same as their tub faucet valve... except that the bottom port (which would have connected to the tub spout) is shut off with a brass plug.

Tub Trivia:

The interesting fact about most modern tub valves, for those of you that want to know how everything works, is the way the water is diverted to the shower head. All you have to do is block the flow of water at the tub spout, and the water will be forced up the shower riser pipe, and out the nozzle. You can do this by covering the spout with your hand, or a washcloth, while the water is running into the tub.

Some older tub faucets use a rotating lever to direct the water northwards. I doubt these would work as described above.

This is a drop-eared elbow. The ears are meant to be mounted to some solid structure, such as a piece of wood blocking. The threaded end will accept the standard L-shaped shower tube, which is installed after the wall surfaces are complete.

I temporarily attached the drop-eared elbow to a piece of 2x4 wood blocking, which was installed between two studs. Then I could easily measure the length of the riser pipe required to connect to the faucet.

Once the length was established, I soldered the riser pipe to the drop-eared elbow. This will connect to the short riser pipe that was attached to the valve body in the first step.

The two sections of riser pipe were soldered.

I could have made the shower riser pipe in just one piece, but there was a good chance that the drop-eared elbow would not be perfectly aligned with the valve body. It just seemed easier to get perfect alignment by mounting the drop-eared elbow to it's wooden support, and making the final connection in the middle of the pipe's length, away from any combustible materials.

Jumping Ahead:

The valve body has been connected to the supply lines.

Note how I used a 90 degree elbow and a 45 degree elbow to arrive at the desired pipe alignment (instead of using two 90's). This arrangement will have less pressure loss.

The supply pipes drop down a couple of feet. From here they will be connected to the new supply lines that will soon be installed beneath the floor.

In the room below, looking straight up. (My neck gets sore just looking at this picture.) The small pipe that comes through the floor is the hot water branch to the shower. The larger pipe (3/4" diameter) is the new supply line for both second-floor bathrooms. Note the sheet metal heat shields used to protect the surroundings from the heat of the torch. The heavier gauge, the better.

After all the new supply pipes were in place, we applied water pressure to the system and checked for leaks. This must be done before the drywall is installed and the pipes are concealed.

See the Installation of the Neo-Angle Shower.

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Written September 3, 2000
Revised (Formatting) December 26, 2004