Estimated reading time: 3 minutes, 15 seconds

Gas Water Heater Failure

By February 24, 2018 Plumbing, Problem Solving

Estimated reading time: 3 minutes, 15 seconds

Typical gas water heater

No hot water is the symptom but what could be the cause. I responded to the home of a client that we did a major remodeling project work for in 2012 which 5 years after installation. What could be wrong? Its a gas water heater, for cryin’ out loud, such simple technology.

My typical triage shenanigans out of the way over the phone, the client confirmed that she had paid her gas bill and the unit was plugged in “Ha Ha”. I decided to respond on a Sunday evening imagining that the pilot had gone out and that it would be a simple 5 minute fix. The air vents all looked clean enough to me.

The pilot was on and the electronic gas control was reading the three slow flashes which indicates normal operation. No typical whoosh of flame after the thermocouple was heated and the temperature was turned up. The thermocouple was not the typical capillary type, this one had wires coming up out of it which looked a little corroded.

Was it the thermocouple or the gas valve?


If it was the gas valve you would think the valve would signal its failure but it was not. If it was the termocouple, it would have signaled that it was the problem (Low Voltage) I did not have a tester for the thermocouple with me but it was staying lit so I figured it was OK. (Faulty thermocouple will typically not stay lit). The darn thing was DOA, AKA, dead in the water.

I called AO smith in the AM and they got me to technical support quickly and were very helpful. They suggested that the thermocouple with the less expensive part but that it may be the gas valve so they sent me both parts with an RA (Return Authorizations).

The fix

Gas water heater valve

Being a minimalist and optimist I replaced the thermocouple first but the darn thing did not stay lit this time. This left me with no choice, I drained the unit, uninstalled gas valve and installed he new one. The moment of truth was a steady slow flashing. whoosh! it started and all was good in the world.

After-Action Review

My hunch was that the old thermocouple was fine and that the gas valve was broken. I did not try that as I had already installed the new thermocouple. There was not a roll out cut off button on the thermocouple which would have made me suspicious. I felt good replacing both parts. I used Ferguson to hep with the RA that the manufacture provided, and I had to return the parts to the company for the credit.

As a final walk around, I checked all of the gas line connections in the area and found one that was lose which concerned me greatly. I have add this to our checklist at the end of projects that we are responsible for.

  1. Happily client
  2. Great story to tell
  3. Great customer service
  4. Learned a new safety inspection to incorporate into our SOP’s

As a follow up whenever I fix a water heater I call to ask, “are you in hot water at home?” and naturally I got a chuckle out of her. What more can you ask for?

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