Water heaters are fairly simple appliances, but when problems arise, they can present an array of confusing symptoms. Because malfunctions can occur in any part of your hot water system, don’t limit your investigation to the heater alone.
An aging water system can carry sediment into a tank, or sediment may collect in flakes of calcium and lime. In electric models, sediment-covered heating elements will burn out quickly. In gas water heaters, sediment accumulates in the bottom of the tank and forms a barrier between the heat source and the water. Not only does sediment make your heater very inefficient, but air bubbles created by the heat percolate through the sediment and cause a continuous rumbling sound. If your electric heater burns up lower elements frequently, or if your heater rumbles, sediment may be the culprit.
To remove sediment, drain as much water as possible from the tank. Then turn on the water supply and allow the new water to flush through the drain valve for a few minutes.
A dip tube is a plastic pipe that delivers cold water to the heat source near the tank bottom. Occasionally a dip tube will slip through the cold water inlet and fall into the tank. When this happens, cold water entering the tank is drawn through the hot water outlet without being heated. To replace a dip tube, disconnect the inlet pipe from the tank. Slide a new dip tube into the fitting and reconnect the inlet pipe.
New water heaters are equipped with magnesium anode rods that prevent rust from developing in the porcelain tank lining. An anode rod draws rust and corrosion to itself rather than allowing it to settle in the tank lining. Usually trouble-free, magnesium rods may become ineffective if the water has a high concentration of dissolved mineral salts. If this occurs, the water will have a gassy odor or taste and the magnesium rod should be replaced with an aluminum rod.
A relief valve prevents a heater from exploding if the thermostat gets stuck. When pressure builds and the water gets too hot, the relief valve opens until pressure is equalized. However, the spring mechanism in some valves weakens with age and the valves release water with any slight variation in pressure. To correct this, simply remove the old valve and thread in a new one.