How to Repair a Pressure Problem in a Thermostatic Shower

Thermostatic showers are one of the inventions that make your home just a little more comfortable. In non-thermostatic shower valves, when a toilet is flushed or a washer is turned on, the drastic temperature change of the water is evident by the bather. In thermostatic valves, a temperature is set to the nearest degree and the valve compensates for any changes in hot or cold by limiting the flow of water to either side. While the thermostatic valve cannot compensate for immense pressure changes, it does an excellent job of regulating temperature.

No matter how good a job thermostatic valves do, they are a device with a lot of integrated parts and like any other similar device there can be problems associated, especially as the valves get older. We're going to look at a few symptoms and how to trouble-shoot them. Remember to shut off the water before taking apart the valve.

Failure to Regulate Temperature

If your thermostatic valve fails to regulate temperature, the first thing to do is to check for dirt in the check valves. Sometimes dirt can inadvertently lodge the check valve open preventing it from closing and just needs to be removed with a cotton swab and cleaned. Another issue could be that the water lines are actually installed backward. Contrary to what you may think, it does matter which side they are installed, as the valve has a hot side and a cold side. Obviously to remedy this you would simply switch the lines back.

Failure of Hot and Cold Water to Mix

The first thing to check is the water pressure at the inlets. If there is a lack of water pressure due to an obstruction, loose fitting, or damaged line the proper mixing cannot take place. The pressure issue will need to be resolved before the valve can operate properly. A partially blocked shower head can also cause this issue. If you feel that the shower head may be partially blocked, take the shower head off, clean the debris and soak in a 50/50 mixture of water and white vinegar to descale the shower head.

Water is Either Too Hot or Too Cold

Again, the first thing to check would be for dirt in the check valves. Follow the procedure above. Calibration may also be an issue. Your thermostatic valve will come with calibration instructions, normally you will remove the face of the handle and there will be an adjustment screw in which you can couple with a thermometer and adjust the setting. The other option would be if the actual water heater setting is not correct, which does not involve the valve, so I will not go into detail on how to alleviate this issue.

Low Water Pressure

This could be caused by debris in the check valve or a blocked shower head and described above but could also indicate debris in the cartridge or a water pressure problem elsewhere. The cartridge is a housing with screens that filter out debris and prevent it from damaging the valve. If the screens get clogged they will need to be cleaned. Not all thermostatic valves have cartridges. To remove the cartridge take of the cover plate, the handle and accompanying o-ring and then use a wrench to unscrew the cartridge.

These are the most common problems with thermostatic shower valves. If you've tried these steps and there is still a malfunction it may be due in part to a faulty or malfunctioning valve or cartridge.