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I have a relatively new water heater (installed by previous owner). I've only been in the house a few months and did not notice this noise until after being there a few weeks. What happens is after any amount of hot water has been run, a loud snapping/clicking noise can be heard from the water heater. Could something be wrong with it?`

Being that it is an electric water heater, I am wondering if it's the heating element turning on. However, like I said, I didn't hear it the first few weeks we were there

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What kind of water heater is it (gas, electric)? If it's gas, could it be an igniter or does it sound like it's coming from somewhere else? –  BMitch Jun 15 '11 at 19:01
    
It is an electric water heater –  Tanner Jun 15 '11 at 19:11
    
is the sound sporadic, or rhythmic? How loud is loud I can hear it all the way upstairs, or I have to be standing next to it, with little to no other sound around me, or I have to put my ear against the heater? –  Tester101 Jun 16 '11 at 12:48
    
As long as there is not too much noise in the house, you can hear it half way across the house. It's a one time noise that won't happen until the next time you run water. –  Tanner Jun 16 '11 at 12:55
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If it's a single click, it could just be a relay turning the unit on/off, or possibly some type of mechanism that says "hey I'm full again". –  Tester101 Jun 16 '11 at 15:53

2 Answers 2

You probably have sediment buildup in the bottom of the hot water heater. Pockets of water get trapped in the sediment/scale at the bottom of the hot water heater, turn to steam when it heats up, then "explode" causing the noises you are hearing.

You could try draining the water heater to get some of the sediment out, but honestly it's probably too late for that - might want to have a pro come out and take a look at it. It's not likely a critical issue, but it would be best to get that scale cleaned off to prolong the life of the unit.

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Why would this only happen when water has just been run? Right now if I go run hot water for 10 seconds then turn the water off, within 20-30 seconds I will likely hear the noise. –  Tanner Jun 16 '11 at 0:09
    
@Tanner: When you run the water, the heater likely turns on to make sure it can supply you with all the hot water you want. It's not smart enough to figure out that you only need 10 seconds of water, it wants to make you happy and make sure you have nice hot water. –  Tester101 Jun 16 '11 at 12:42

As Eric has said, this is almost certainly being caused by sediment build-up. The sediment is wet, and when the element turns on, it turns the nearby water trapped by the sediment into steam, and it pops. It's not very much different than popcorn popping.

I've copied the appropriate steps from another answer of mine (didn't want to link it since you only need to do about half of what the other guy needed to do.)

Flushing your water heater:

  1. Unplug your water heater.
  2. Attach a garden hose to the drain at the bottom of the water heater.
  3. Run the other end of the garden hose outside.
  4. Open the drain.

This will forcefully drain the water heater, and hopefully the city's water pressure will be able to get a decent amount of the sediment out of the bottom. Depending on how fast the water is flowing, let this continue for 1-5 minutes. Sometimes the drain can be pretty clogged up or the bottom quite full, and the water won't come out very fast, especially when you disconnect the city's water pressure.

If this does not solve your problem, you'll need to be ready to replace the water heater (the bottom element will fail if buried under sediment, and no bottom element means basically no hot water)... or you can do a more thorough cleaning by taking the bottom element out (see other answer for instructions) and wetvac'ing the sediment out, like so: www.youtube.com/watch?v=pt1M7qO6Lh8

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