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Why is My Water Heater Making a Popping Noise?

Very few people give their water heater much thought–until something goes wrong. If you start hearing noises from your water heater, or hot water taps, it is time to pay attention and figure out what is happening.

Popping noises coming from your water heater are a sign of a problem getting ready to happen. You may also hear other noises that are signs of bad things to come. Here is an explanation of where popping noises come from, what causes them, and what to do about them.

Water heater behind hvac system
Water Heater Wedged in Corner. Difficult to Flush Properly.

 

 

Water Heater Popping Noises

You probably do not spend much time around your water heater, so the chances of hearing noises is reduced. It may be instructive to spend a little time close to it while someone is running hot water long enough to get the tank to run through an on/off heating cycle.

 

What is the Cause of Water Heater Popping Noises

Water heater popping noises almost invariably are caused by sediment build-up. On the bottom of the tank of gas-fired tanks and on the elements of electric water heaters. This sediment traps water close to the bottom of the gas-fired tank and against the elements of the electric heaters.

The water next to the heat source gets hot first and bubbles through the sediment, popping as it escapes. The popping sound is not the problem. Sediment build up is the problem.

 

How to Stop Water Heater Popping Noises

To stop the popping noises, and save on heating costs, and extend the life of the tank, you will have to remove the sediment.

 

Removing Sediment from Gas-Fired Water Heaters

This is a drain and flush the tank operation–not difficult, just time consuming.

  1. Turn off the breaker in the panel. (I know it is probably only a 12 volt igniter so you will not get much of an electrical shock. But a little bit of gas or propane leakage and a spark could ruin your day.)
  2. Turn off the fuel supply.
  3. Turn off the cold water intake.
  4. Connect a piece of hose that reaches floor drain to tank drain tap.
  5. Open the drain valve and at least one hot water tap (to allow air into the system).
  6. When the water has drained out, open and close the cold water intake a few times and let that water drain out. This should float the sediment out. (Note: Our water has enough undissolved solids in it that I close the tank drain tap when empty, disconnect the cold water intake pipe, and funnel a couple of gallons of vinegar into the tank to loosen the sediment. Then half fill it and drain it again.)
  7. Once the water is running as clear as you can get it, close the drain tap and disconnect the drain hose.
  8. Open the cold water intake to fill the tank. (When water begins running out of the hot water tap, the tank is full.)
  9. Turn on the fuel supply and electrical supply and start the tank. It will take a while to heat the entire tank of cold water.

 

Removing Sediment from Electric Powered Water Heaters

Although most of the sediment will attach to electric elements, there is still some in the bottom of the tank. And draining the tank makes element removal easier so you can follow the instructions above for draining and flushing the tank.

  1. Make absolutely certain to turn off the breaker. You are likely dealing with 240 volts, not 12. Making it a little more dangerous.
  2. Drain and flush the tank.
  3. Before refilling the tank, remove the heating elements. (There are usually 2–one upper and one lower.)
  4. Soaking the elements in vinegar, CLR, or some type of descaler should get them clean. (Note: It may take a few soakings if they are really scaly.)
  5. Replace the elements ensuring you use Teflon tape to prevent leakage. 
  6. Fill your water tank and turn on the power. The heating elements should start working immediately. (Electric tanks usually take quite a while to heat when the water is all cold.)

Note: If your heating elements are more than 5 years old, or you cannot get the elements clean, you may want to give some consideration to replacing them while you have them out. Generally a pair of elements costs less than $50.00, giving you the peace of mind that the new ones will not fail.

 

More Water Heater Noises to be Aware Of

Water heaters make all kinds of other noises. Many of them are related to sediment. Some aren’t.

 

Water Heater Making a Gurgling or Rumbling Noise

A gurgling noise coming from your hot water tank is likely caused by even thicker layers of sediment settled on the bottom. (Some times it gets thick enough to cover the bottom electric heating element.)

  • Gurgling. Gurgling noise occurs when the build-up becomes thick enough that water being forced through it does not pop, but causes a gurgling sound.
  • Rumbling. You will likely hear rumbling noises when the sediment build-up becomes even thicker. At some stage of sedimentation, pieces of the crust will break off, be forced to the top of your tank, then make a rumbling noise against the sides of the tank as they fall back to the bottom. (Undissolved solids containing calcium or magnesium are particularly bad because they are heavy.)

Note: If your water is prone to quick and heavy sediment build-up, drain and flush your tank every 6 months. This will also save money because your water heater will be heating water, not sediment first.

 

Water Heater Making a Running Water Noise

If you hear a running water noise close to your water heater, start looking for a leak. Leaks are more common in CPVC pipes than in copper or PEX piping. (CPVC piping is more vulnerable to breaking from expansion and contraction,) 

Check your overflow pipe for leakage, specially if you have it connected to the floor drain and cannot see if it leaks. Overflows are more prone to leaking in older water heaters because they tend to overheat. 

 

Popping, Vibrating, or Hissing Noise When Tap is Turned On

These sounds, when heard through the tap, are an indication of sediment build-up. The popping, gurgling, and hissing noise you hear when standing beside the tank is changed a bit to popping, vibrating, or hissing by the time it gets to the tap. Same problem. Same cure. Sediment build-up on the tank bottom. Drain and flush the tank more often.

 

Miscellaneous Water Heater Noises

Here are some of the other noises you may hear from your water heater.

  • Sizzling, Crackling, or Hissing. These noises also point to excessive sediment build-up in electric tanks and internal condensation in gas fired heaters. In an electric water heater, the sounds are caused by the lower element being covered by sediment. The build-up of heat forces water through the glop–making the noises you hear. These sounds coming from a gas fired heater likely means your tank is leaking and water is dripping onto the hot burner pan.
  • Ticking. Ticking sounds can come from sudden water pressure changes, a normally operating heat trap nipple, or expanding pipes hitting loose pipe straps.
  • Singing, Screeching, or Screaming. These noise indicate a water flow restriction in the water heater tank–often at valves. Specially the Temperature and Pressure Valve. This is like the valve on your pressure cooker and provides protection for the water heater if it gets too hot.
  • Hum . . . Again. If you have an electric water heater, make sure the elements are tight. A loose element will make a tuning fork type humming sound.
  • Tapping or Ticking. If you tank is equipped with check valves, you might hear a tapping sound as water temperature changes in the valve. This is completely normal and should cause you no worries.

Note: Keep in mind that people’s perceptions and descriptions of noises can be different. Your rumble might be my vibration. My scream might me your squeal.

 

Call a Plumber

When all else fails, or you do not feel comfortable taking on plumbing problems, call a reputable plumber. Yes, it may be more expensive now, but it could be much more expensive if you wait.

Most of the noises you hear from your water heater are not signs of an impending catastrophe. More like a slow-motion train wreck. If left unattended to, the noises will eventually turn into something more serious.


Terry Schutz

I have worked as a contractor, sales person, and business owner in the construction industry for over three decades--mostly in home renovations and also as a home builder. I have been married to the same wife for 46 years. We have 3 children and 4 granddaughters. I have also been writing semi-professionally for about 20 years--construction articles, personal stories, and politically incorrect social commentary.


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