As with any faucet brand, a Moen shower valve contains working parts that can go bad over time. Moen pressure-balance shower valves are designed so they sense hot and cold water pressure and keep them in balance, preventing the shower from sudden surges of hot or cold water. When the shower valve begins leaking or no longer correctly balances the hot and cold water, fixing the problem is usually a simple matter of replacing the insert cartridge.
Before You Begin
Many single-handle Moen shower faucets use the same replacement cartridge, #1222, which makes replacement quite easy. Most replacement cartridges use a plastic design, but there are also solid brass heavy-duty models, which are designed for commercial use but will also provide a very long life when installed in a residential shower. Genuine Moen replacement parts are widely available, but there are also less expensive aftermarket cartridges made by reputable manufacturers.
Some Moen shower valves have a temperature limit stop device that prevents accidental scalding by limiting how far the handle can turn in the hot direction. You can adjust the setting of the limit to fine-tune the temperature for your shower.
Setting up the scald guard is easy, but you may have to try it a few times before you get the temperature where you want it. The water supply can be on while you set up the scald guard, but the handle and handle adapter must be off.
- To turn the water temperature down, move the outer white piece to the right to limit the hot water. The number of splines you move will depend on how much restriction you want. Try turning the valve on with the handle adapter loosely in place until you find the temperature you want.
- To turn the water temperature up, move the outer plastic piece to the left a few splines.
Note: Be careful when testing. Turn the hot water on slowly so you can stop before it gets hot enough to scald you.
Source: The Spruce