Where the noise comes from

Hard water leaves calcium carbonate and other minerals in the bottom of a tank as it is heated, year after year. On a gas heater, the burner heats the tank from below, and water trapped under the sediment layer flashes to steam in small bursts. That is the popping you hear.

Sediment also takes up space, so the tank holds less hot water, and it insulates the bottom of the tank from the burner. The heater runs longer to do the same job, and the steel under the sediment can run hotter than it should.

How sediment problems usually develop

Early years
Thin layer of sediment. Annual flushing removes much of it and keeps noise away.
Middle years
Occasional popping during heating. Hot water may run out a little sooner.
Later years
Loud rumbling, longer recovery, rusty or cloudy hot water, and a drain valve that clogs when opened.
End of life
Hardened sediment that will not flush out, plus corrosion. Replacement is usually the practical answer.

What a typical tank flush involves

Follow the heater manufacturer's instructions. If you are unsure, have a plumber do it.

  1. Turn off the heat.Gas control to Pilot or Off, or the breaker off for an electric unit, and give the water time to cool.
  2. Close the cold inlet.Shut the supply valve at the top of the tank.
  3. Attach a hose to the drain valve.Run it to a floor drain or outdoors where hot, cloudy water will not cause damage.
  4. Open a hot tap and the drain.Opening a hot faucet lets air in so the tank drains. Watch for sediment in the discharge.
  5. Flush with short bursts of fresh water.Briefly open the cold inlet to stir and rinse the bottom until the water runs clearer.
  6. Refill completely before reheating.Close the drain, open the inlet, and wait for steady flow at the hot tap before turning the heat back on.

Should you flush or not?

  • IfThe tank is fairly new and flushed regularlyThenKeep flushing on the manufacturer's schedule.
  • IfThe tank has never been flushed and is several years oldThenAsk a plumber to assess it first; a first flush can loosen a lot of material.
  • IfYou see rusty water or the tank is near the end of its warrantyThenGet a replacement quote alongside any maintenance.
  • IfThe noise is a high-pitched whine or screechThenThat is often a valve or flow restriction rather than sediment; have it checked.

Questions to ask your plumber

  1. How much sediment did you find, and is the anode rod worth checking or replacing?
  2. Is the drain valve in good shape, or should it be upgraded?
  3. How often should this tank be flushed with our water?
  4. Is the noise worth addressing on a tank this age, or should I plan for replacement?

Common questions

Is a popping water heater dangerous?

Popping itself is a symptom of sediment rather than an immediate hazard, but it means the tank is working harder and the bottom may be overheating. Have it looked at and keep an eye on the relief valve.

Do electric water heaters get sediment too?

Yes. Sediment can bury the lower element, which may cause it to fail and make the tank run out of hot water sooner.

What is an anode rod?

A metal rod inside the tank that corrodes instead of the tank. Checking it during maintenance can show how much protection is left.

General information for Golden Hills, not a quote or professional advice. In an emergency, call 911.