Sediment Buildup

• If sediment builds up at the bottom of your heater, the sediment can trap tiny pockets of water as the water makes its way through the heater. When the heating element turns on, the trapped water turns to steam. This causes a clicking or popping noise. The noise often occurs right after turning off the water because the heater is still attempting to heat water for a few minutes after the water has been turned off.
  
  

Pipe Expansion

• Some water heaters use vent pipes that are made of more than one type of material. For example, double-walled piping may have an interior wall made out of aluminum and an exterior made out of another type of metal. When the heated water goes through the pipes, the interior wall may expand due to the heat while the exterior wall doesn't. The expansion can cause a ticking sound.
  
  

Water Hammer

• Water hammer is a serious problem in which water hits the pipes with unusual force, causing a loud ticking or banging noise. This problem is usually caused by water pressure problems or by blockages in the pipes. If left untreated, water hammer can cause pipes to burst. Ticking sounds can also be caused by air pockets in the pipes, but if the sound occurs after turning off a faucet or valve, the problem is more likely water hammer.
  
  

What to Do

• If your water heater is ticking after you shut off the water, drain the water heater to remove any sediment built up in it. Unplug the heater, attach your garden hose to the bottom and open the drain. Make sure the other side of your garden hose is outside so you don't end up with a mess in your home. After about five minutes, the heater will drain along with the sediment. If you continue to have ticking noises, ask your plumber to inspect your pipes to help determine the source.