The introduction of air into a hot water heater and hot water lines will inevitably lead to problems. The most minor of the problems will manifest in the form of air emitting from the faucet whenever you turn on the hot water, or the water may spit and sputter. Air in your hot water system can also lead to more serious problems. Air trapped in the hot water heater itself could lead to excessive temperatures and pressure, which will cause the pressure relief valve to activate. Fortunately, bleeding air from your hot water lines is rather simple.
Locate the drain valve on your hot water heater. On most tanks, the drain valve is situated near the base of the tank. The valve may be constructed of either plastic or metal. Turn the valve on the drain clockwise to ensure that it is tightly closed. If the valve is opened slightly, it may be allowing air to enter the tank and your water lines.
Locate the cold water pipe that feeds cold water into the tank. The cold water pipe is connected to the top surface of the hot water tank. Many newer tanks will also indicate which pipe supplies the cold water. The cold water pipe will have a valve nearby. Ensure the valve is fully open. If the valve is not completely open, water will not adequately fill the tank, which may lead to the formation of air pockets.
Open all hot water taps in your home, beginning with the tap closest to the hot water tank. Continue turning on the hot water at sinks and bathtubs throughout the house. Allow the hot water taps to remain open until all air is out of the system.
Close the hot water taps, beginning with the tap furthest away from the hot water tank. Ensure the hot water is flowing steadily from the faucets, without being interrupted by bursts of air, before you begin turning off the hot water.
If the problem persists, you may have an issue with the water lines in your home. Check the cold water pipe, as well as the shut-off valve, connected to the hot water heater. If the line is improperly installed, the line leaks or the valve does not function correctly, it could lead to air forming in the water heater. Also check to ensure the hot water lines between the tank and your sinks/tubs are properly installed and leak-free.