Showering With Too Much Water
Older shower heads put out twice as much water as the new shower heads. Check your shower head. If it has a flow of 5 gallons per minute, replace it with a shower head that has a flow of 2.5 gallons per minute. This doubles the length of time you can take a shower.
Your Water Heater Is Too Small
The most common reason for running out of hot water too quickly is that the water heater doesn't handle enough water for the number of people using it. The larger the family living in the home, the more hot water you will need. A 30-gallon heater may work for a couple, but a family of four might use a 50-gallon heater.
Check Your Hot Water Heater
The hot water heater might be causing your problem. The dip tube on the cold water inlet might be broken or worn out. This would prevent using the water at the bottom of the tank, thus cutting the effective capacity of the hot water heater in half. If you have an electric hot water heater, one or both heating elements could be out. Hit the reset button to see if that restarts the elements. If not, you may need to replace the entire water heater. In gas heaters, the efficiency of heating depends on the size of the burner. If the burner's too small to keep enough water hot for you, consider buying a larger heater.
Check the Temperature Setting
The higher the temperature setting on the water heater, the faster it heats water, which makes more hot water available. The problem is that the higher you set the temperature, the higher your gas and electric bill will be. In addition, setting the temperature too high might cause you to burn yourself.
Insulate Your Water Heater
Much of the heat from the water may be escaping through the sides of the water heater, allowing the water to cool. Insulate your water heater to keep the heat in the water, where it belongs.
Flush the Water Heater
Flush your water heater occasionally to remove sediment from it. Sediment at the bottom of the tank adds one more thing the heat has to get through to reach the water and heat it. Flushing out sediment is especially important if you have a gas water heater.