DEAR MIKE: I have an old single-handle shower valve that I want to replace with a modern one. How difficult is this project? -- Wes C.
DEAR WES: This project is very challenging, and I would make sure your skills are such that you can overcome the pitfalls, yet be man enough to call someone for help if you need it. This all translates to starting early in the day.
You are going to install a balanced pressure valve. This device protects you in case there is a sudden drop in cold water. For example, if someone flushes the toilet, you won't get scalded. Instead, the valve will quickly reduce the hot water pressure to maintain the ratio of hot to cold water.
The shower valve is located inside the wall behind the shower handle. You will have to gain access to the valve to replace it. If the escutcheon plate behind the shower handle is large enough to cover the hole, you're in luck.
Typically though, you have to open the wall so that you can get a torch in the opening either to sweat out or cut out the old valve. If you're starting to get the idea that this is a surgical procedure, you're right. I imagine it's something like heart transplant surgery.
When you see the valve, it's going to have three or four pipes connected to it. If this is a shower only, you will have three copper pipes attached to it (one on each side and one at the top); if it is a tub/shower combination, you will have four pipes connected to it (the additional pipe at the bottom flows water to the tub spigot).
The interior walls of your shower will be covered in tile, a surround or some other watertight material. If you're going to cut this to enlarge the access hole, you may have a problem finding, for example, replacement tiles if you break one.
Sometimes the best course of action is to cut open the back of the wall. It's easier to repair drywall, and you can give yourself a larger hole in which to work. Often, the back of the wall lies in a closet or some other less conspicuous place.
You will also need to buy a handful of various fittings that aren't supplied with the new valve. On a typical valve, you will have four female openings into which you will screw male adapters. If your shower does not have a tub combination, you will need to buy a threaded plug and close up the bottom outlet of the new valve.
Turn off the water to the house before you begin and open the shower valve to relieve the water pressure.
With the old valve exposed, you will need to map out a plan. Depending on how the old valve was piped in, you may be able to sweat the old valve out or you may choose to cut it out.
The best you could hope for is to have a length of straight copper pipe attached to all points entering the adapters. In other words, you don't want any elbows right next to the adapters. Not that elbows make for an impossible installation, but straight pipe gives you a little more flexibility. Ideally, you could cut through the straight pipe, leaving a void where the new valve will go.
You will solder short lengths of copper pipe to the adapters of the new valve so when you hold the new valve into the void, the ends of the cut pipes fit together nicely.
So you might ask how to connect all of these cut pipes. The answer is with a repair coupling. A repair coupling is essentially a sleeve that fits over the two pipes. There is no internal stop in the coupling which allows you slide the coupling all along the length of the pipe.
Push a repair coupling onto the end of the pipe and slide it out of the way (clean the inside of the coupling with a wire soldering brush first). Place the valve into position and slide the repair coupling down the pipe until it covers the joint of the two mating pipes. Repeat this for each pipe connection.
You must remove the shower cartridge in the valve or risk damaging the cartridge from the heat of the torch. This is just a matter of removing a pin and pulling the cartridge out. Clean and flux the mating pieces, then solder all the couplings. For information on soldering, visit my Web site.
Since you will be working in a small opening, you may want to purchase a flame cloth to minimize the possibility of fire. Have a bucket of water and a fire extinguisher nearby just in case. Reinstall the cartridge and turn the water back on and check for leaks.
The last step is to repair the wall. If you chose to open the wall behind the shower, you can repair the drywall or buy an access door. This is a small door that will allow you access if any future problems develop. Conquer this project and you can enroll in med school.