How to Get Your Water Heater to Stop Dripping Water
Water observed leaking from the temperature/ pressure relief valve (T&P) or connecting runoff tube (located on the side or top of the tank) may be the problem, and can be caused by several different factors, first of which, may be a malfunctioning T&P valve. More often though, the leak is caused by excessive temperature or pressure.
The T&P valve is a safety feature installed on the water heater to prevent the tank from possibly exploding if temperature or pressure would build to unsafe levels. These valves are normally set to release at 150psi or 210F. Because of the potential for this type of dangerous discharge occurring from the valve, an appropriate sized tube is extended close to floor level to minimize chance of injury should the relief valve activate.
To troubleshoot, the setting on the control valve located at the front bottom of the tank is checked. If the service manual is still available, a check can be made to see what corresponding temperature the dial is set. If the manual is not available, there is normally a triangle, hash mark, or arrow which stands out and usually indicates 120F. Normally this setting would supply an adequate amount of hot water. A thermometer used at a sink spout is can determine if the water temperature matches the setting. If the tank is instead turned to the high setting, it may be causing the leak or drip at the water heater’s T&P valve.
The second and more common reason for this leak or drip is excessive pressure coming into the tank combined with pressure building within the tank as the water is heated and expands. A water pressure gauge is used to determine the water pressure coming into the house. Normal pressure is around 50-60psi. If water pressure is high, a pressure regulator must be installed, preferably near the main water service point of entry into the house. This will reduce excessive incoming pressure. Although this may cure the dripping T&P valve, it may itself not be enough. In addition to the reducing temperature and installing a pressure regulator, a device known as a thermal expansion tank may need to be installed.
Many water authorities are now requiring a mechanism called a back-flow preventer or check valve be installed on the incoming water line. A back-flow preventer is designed to help prevent any pollutants from a given building’s potable water contaminating the public water supply. A byproduct of these mechanisms is that they also create a closed system, not permitting water to expand back into the main water service as thermal expansion occurs when water heats within the hot water tank. This can build high pressure within the water heater and cause water to drip from the T&P valve thereby relieving the excess pressure. To compensate a device known as a thermal expansion tank is installed on the cold water side of the water heater. As the water heats, a bladder of air inside the expansion tank compresses to minimize the pressure increase within the system and prevents the T&P valve from leaking.
I hope this article has shed some light on the causes and cures for the dripping T&P valve and given you enough information to make an informed decision as to repair. If a leak is observed in places other than the T&P, a new tank may be needed.
I would advise that all diagnosis and repairs to a water heater are completed by an individual trained and certified to complete such repairs.
