Why is my water heater making strange (rumbling, gurgling, knocking or banging) noises?

Friday, August 10, 2018

We have even heard it called a burping sound. Fixing the problem is as simple as draining the sediment/mineral buildup from the tank, which is the cause of the problem and also the purpose of a small faucet at the bottom of the tank. When there is a heavy layer of crud on the floor of the tank, heat is trapped under it that intermittently pushes through the layer and escapes with a bubbling—or sometimes even a wheezing—sound effect. Here’s the steps to follow to get your silent water heater back: 

  1. Shut off the the water heater, either by turning the thermostat dial on a gas water heater to “PILOT,” or turning off the breaker on an electric water heater. 
  2. Attach a garden hose to the faucet at the base of the water heater. Run the end of the hose outside to a location that will not be harmed by the hot water, which can kill grass or the roots of landscape plants where it drains. If you can’t easily find a satisfactory spot for the hot water to drain without damaging your yard, then run the hot water at sink for a while until it cools down.
  3. Close the valve on the cold water supply pipe of the water heater, to shut off the water flow to the tank.
  4. Open a hot water faucet at a nearby sink. This will allow air flow backwards into the tank so that it will drain easier.
  5. Open the hose faucet valve and let the tank drain completely.
  6. Close the hose faucet and let the tank refill, leaving the sink faucet open for a while. You will get a sputtering mixture of water and the air that is being pushed back out of the tank for a while. When the water runs continuously at the sink, without any sputtering, shut off the sink faucet.
  7. Turn up the thermostat on the gas water heater, or switch on the breaker at an electric water heater, put the hose away, and you are done.  
  8. If the hose faucet drips and does not close completely, there is likely some sediment residue stuck in the valve. You may have to repeat the flushing operation one more time.

   It’s a sensible maintenance idea to drain your water heater every two years, which will both prevent the annoying sounds and extend the life of the tank. If the flushing operation is more than you want to tackle, a professional plumber can do the job for you, along with a doing a general maintenance check to make sure there are no other problems.

    Also see our blog post Why is there water in my water heater drain pan?

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Here’s links to a collection of more blog posts about WATER HEATERS:

Are water heaters required to be raised off the floor? 

Can a Temperature and Pressure Relief (TPR or T&P) valve be mounted to discharge horizontally?

Where are gas water heaters not allowed to be installed?  

Is the minimum size water heater inlet pipe 1/2" or 3/4" according to the building code? 

Can you use a light switch for a water heater disconnect? 

How can I tell if a water heater is HUD-approved for mobile/manufactured homes?

Can you wire a 240-volt water heater with 120 volts? 

Is it alright to have a shut-off valve on both the hot and cold water pipes at a water heater?  

What is the minimum clearance to doors and windows for an outdoor tankless gas water heater? 

What is required clearance for access and working space in front of an electric water heater? 

Why is the water heater older than the house? 

Does a water heater need a shut-off valve? 

Why should a tankless water heater have an isolator/service valve kit installed?

When was a gas water heater first required to be elevated 18 inches above a garage floor?  

Can the temperature and pressure relief (TPR) valve discharge pipe for a mobile/manufactured home water heater terminate under the home? 

What is the purpose of a thermostatic mixing valve above a water heater? 

Does a tankless gas water heater still work with no electricity during a power outage?  

•  Why do water heaters have a sacrificial anode? 

What is the difference between a manufactured/mobile home water heater and a regular water heater? 

Does a tankless water heater require a pressure relief valve?

When is a water heater drain pan required?

Why is there water in my water heater drain pan?

What does it mean when a water heater Temperature/Pressure Relief (TPR) discharge pipe is "trapped"? 

Can I leave a gas water heater in place when remodeling a garage into a family room or bedroom? 

Where do I find the water heater in a mobile home?

Does a tankless water heater in an attic require a drain pan? 

Does an electric water heater require a disconnect? 

Is a catch pan and drain piping required for a replacement water heater?

What is the difference between a single element and dual element electric water heater? 

What is an FVIR water heater?

What is a heat pump water heater?

What is a dielectric union?

What's that powdery crust on the pipe connections at the water heater? 

What are the most common installation mistakes with water heater replacement?

What can I do to make my water heater last longer?

How can I determine the age of a water heater if the serial number is missing or decoding it is impossible? 

How does a hydronic heating system work?

What is the difference between a regular water heater and a direct vent water heater? 

What is the difference between a regular water heater and a power vent water heater?

What is backdrafting at a gas water heater? 

How do I determine if a water heater is gas or electric?

What does it mean when a gas appliance (water heater, furnace, or range) has been "red tagged"?  

• What's the valve with the flip-up handle on the water heater for?

• Why is an older water heater an insurance problem?

   Visit our WATER HEATERS page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles. 

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