How to Replace a Shower Cartridge
Ask This Old House plumbing and heating expert Richard Trethewey travels to Seattle to help a homeowner whose shower runs cold whenever there’s a demand for hot water elsewhere in the house
- These instructions apply to the earliest models of single-handle shower valves. Follow manufacturer’s instructions for your specific style of valve.
- Start by removing the handle of the shower. There’s usually a cover plate that can be pried off with a flathead screwdriver. Then, hold the handle tight and unscrew the screw behind the cover plate with the same screwdriver.
- Remove the escutcheon plate by unscrewing it.
- Look to see if there’s a water shutoff near the shower valve. If not, shut the water off at the main water supply line.
- There’s a small clip holding the cartridge in the shower valve. Carefully pry that up.
- Use a cartridge removal tool to carefully work the old cartridge back and forth until it can be safely removed from the wall. The cartridge removal tool may be included with the replacement cartridge.
- Once the cartridge is loose, use a pair of pliers to carefully pull it out of the wall. Don’t force it out. If it gets damaged while being removed, it could destroy the whole valve and then the entire thing will need to be replaced.
- Put some grease on the replacement cartridge and carefully work it back into the valve.
- Put the small clip back in to hold the new cartridge in place.
- Add a bead of silicone and a foam bead around the back of the escutcheon plate to make a watertight seal.
- Screw the cover plate and the shower handle back into place.
- Turn the water back on.
Depending on which company manufactured the valve, there may be some variations to how the valve cartridge is replaced. This homeowner had a Moen valve and the replacement parts were manufactured by Moen. They can be found at most home centers and plumbing supply stores. They sometimes come with a cartridge removal tool, so it helps to get the replacement cartridge before starting the work.
The screwdriver and pliers Richard used can be found at home centers.