Why is my water heater making a popping noise?
Popping, rumbling, or kettle-like sounds from the tank during a heating cycle, often loudest after heavy hot water use.
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Key takeaways
- This is usually not an emergency, but it does not fix itself and it gets worse if you leave it.
- Most likely cause: Sediment and mineral scale on the tank bottom.
- Do this first: Note how long the noise has been happening and whether it is getting louder.
- Call right away if the noise comes with water pooling under the tank.
- The repair starts with: Shut down the heater and drain the tank.
What it is
Water heater popping noise A popping or rumbling noise from a water heater is the sound of water trapped under a layer of mineral sediment on the tank floor boiling and bursting through as the burner heats the tank.
It is not an emergency, but the sediment buildup causing the noise reduces efficiency and can shorten the tank's life if it is never flushed.
The short answer
Popping and rumbling from a water heater is caused by sediment. Mineral scale settles on the bottom of the tank, water gets trapped underneath it, and the steam bubbles escaping through the layer make the popping sound. Denver area hard water makes this common. It is not usually an emergency, but it overheats the tank floor, wastes fuel, and shortens the life of the heater, so it should be flushed rather than ignored.
What it usually means
These are the causes we find most often, ranked from most likely to least.
- 1
Sediment and mineral scale on the tank bottom
Most likely
Hard water leaves a layer that traps water and boils it into steam.
- 2
Overheating from a thermostat set too high
Common
Higher temperature accelerates scaling and increases the noise.
- 3
Scale buildup on electric heating elements
Common
Elements crusted with scale sizzle and pop during every cycle.
- 4
Failed anode rod allowing accelerated corrosion
Less common
Once the anode is spent the tank itself starts to degrade.
- 5
Tank at end of service life
Occasional
Heavy long term sediment often signals the tank is close to failing.
What to do right now
- 1Note how long the noise has been happening and whether it is getting louder.
- 2Check the thermostat setting and lower it if it is set unusually high.
- 3Look for any moisture around the base of the tank.
- 4Schedule a flush rather than waiting for the noise to stop, because it will not.
When it is an emergency
- The noise comes with water pooling under the tank.
- The relief valve is discharging.
- You smell gas or see soot around the burner area.
What the fix involves
The standard fix is draining and flushing the tank to remove the sediment layer, checking the anode rod, and setting the thermostat to a safe and efficient temperature. Where the tank is heavily scaled and near the end of its life, replacement is the better value than repeated flushing.
- 1Shut down the heater and drain the tank.
- 2Flush the sediment and clean the elements where applicable.
- 3Inspect and replace the anode rod if it is spent.
- 4Refill, set the temperature, and check for leaks under pressure.
What drives the cost
Every job is quoted before work begins. These are the factors that move the number on this kind of repair.
- Flush and service versus full tank replacement
- Tank size and fuel type
- Anode rod and element replacement
- Access to the tank and drain point
Related problems homeowners ask about
Why do I have no hot water?
Taps run cold at every fixture, or hot water disappears after a minute or two. The heater may be silent, or it may run without ever heating the tank.
Read this nextWhy is my water heater leaking from the bottom?
Standing water under the tank, a damp ring on the floor, or rust streaks running down the outside of the jacket.
Read this nextWhy is my water brown or discolored?
Water runs brown, yellow, or reddish, sometimes with visible grit, and it may stain fixtures and laundry.
Read this next
Read more on this
This page is for triage and dispatch. These guides go deeper on how the work is done and what shapes the price.
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- Colorado Master PlumberLicense MP-18927
- Colorado State Plumbing ContractorLicense 2110
- Family Owned & OperatedServing Denver since 2006, 20 years
- Better Business BureauAccredited Business, A+ rating
- Angie's List Super Service Award2012 through 2017
- Serving Denver since 2006Residential and commercial properties across the metro
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