If your shower water is not hot enough or never gets hot, there are several potential problems. Some are very common and simple to fix; others require more attention by a professional. If you are experiencing cooler water temperatures, look at a few signs first to find out what is going on.
Shower Cartridge Issues
A lack of hot water in just your shower is a sign of a problem with the shower faucet. Inside the faucet is a cartridge that mixes hot and cold water together to form the warm water you bath in. If this part breaks or the surface of one of the discs inside the cartridge scratches, it will not operate properly. The result is cool water when it should be hot. To fix this, replace the cartridge by taking off the handle to the faucet, removing the bonnet or retaining nut, and installing a new faucet cartridge. If this doesn't fix the problem, you might have a water heater issue.
Water Heater Turned off
If all the faucets in the home have no hot water, the problem most likely belongs to the water heater, which is the device that heats up the incoming water to the home. The water heater may be turned off. Check the circuit box to see if the circuit switch labeled "water heater" is set to "Off." If it is, turn it back on and wait about an hour for the water heater to heat your water. Try the shower again to see if the water is hot.
Water Heater Malfunctioning
If the water heater break is on, the water heater may have a bad element. This is the part inside the water heater that actually provides the heat. It is similar to an oven element. These parts need replacing after normal usage. The water heater must be drained through a hose or with a drainage pan. The heater is then taken apart and the elements removed and replaced with new ones. This project is involved and usually is best left to a professional unless you are experienced enough to handle it yourself.
Shower Faucet Scald Guards
Some shower faucets have scald guards or temperature control features, which raise or lower the overall temperature the faucet delivers. If you lack hot water in just the shower, take off the handle to the faucet by removing the set screw and pulling it off. Look for a round dial on the end of the faucet, right under the handle. Adjust the dial to increase the temperature of the faucet. Adjusting the dial allows more hot water to pass through the cartridge in the faucet and therefore will increase the total overall temperature of that particular shower.