One word: Thermocoupler.
Here’s the scenario: evening shower time and the water starts off lukewarm. Uh oh. Go to the water heater -which is natural gas, btw – and feel the hot pipe to find it’s also lukewarm. Next, pull off the plate of the bottom and look for pilot.
Uh oh again, it’s not there. This is where it got tricky. You shouldn’t have to hold the pilot down for more than a minute, yet at the three minute mark it still wouldn’t hold. Now, to be frank, I am not a plumber and have never been. However, a bit of mechanical knowledge can be dangerous and given that it was late on a Saturday, was left with no choice other than trying to figure it out. Having an understanding of what a thermocoupler is would be helpful. The pilot light sends a signal through solid copper wire to the heater controls(the thing with the dial on it that sets the temperature of the water). If there is no pilot, it SHOULD NOT turn on the gas and attempt to fire. The reason you hold down the pilot button for a minute is to allow the heat from the pilot to travel through the copper wire to the controls which say “Ok, the pilot is on, keep the gas flowing to it”. If that copper wire is somehow disconnected through lets say this piece below, you have a problem. Not wanting to call in a plumber just yet for a Sunday call would have been real pricey, I called home depot to see what they charge to install a whole new heater. The installation cost alone – $432. Add another $575 for a heater of this size and capacity. Fact was, I had no idea what was wrong and believed it could be a simple repair. Time to get the troubleshooting guide out! The State Industries Hot water heater page contained a troubleshooting guide. After reading the potential causes of no pilot decided it might be the thermocoupler.
I should have taken a picture of the thermocoupler as part of the original assembly and apologize for not having done so. When you’re in the middle of these things, you don’t think about blogging, you just want to fix it. The guy at home depot said prior to replacing the thermocoupler, I should try cleaning the original with some emery cloth. So, I shut the gas line, shut the valve on top of the heater control and removed all of the fittings on the bottom of the controls. One is the copper thermocoupler, one is the gas supply for the burner and the small aluminum one is the pilot supply. After pulling the burner out I realized it was a lot like a bbq burner if you’ve ever seen one of those. So, I cleaned the thermocoupler, put it back together and nothing…
Onto the replacement. Pulled the burner back out from under the heater and took it to the garage for inspection. Turns out the new thermocoupler was different. It didn’t have a break in it where the safety was(see picture above). For you car guys, it looked a lot like a copper oil pressure line. After removing the old thermocoupler, I realized that the new one fit nicely, but was loose, so I had to improvise by bending the mounting tab slightly to put pressure on it. Then, since the old copper line was threaded through the grommet, I had to slice the grommet to fit the new one(see image below, it’s the small one with three lines through it). Literally, in 15 minutes, I put the new one in and wala, hot water. It worked near instantly. The pilot held in 20 seconds and the burner came on immediately. What could have been a very expensive day wound up costing $12.23 including tax by installing a “24 inch universal thermocoupler”. I was prepared to replace the entire heater which was well over $500 and would have taken me a few hours.
One thing I cannot stress enough is that if you are not a real mechanic- one with boxes and boxes of tools who has replaced damn near everything, or a plumber, please don’t try this repair. I’m not a plumber either but was prepared to replace the entire thing and am an excellent mechanic who has an deep understanding of how things like valves and thermocouplers work. Not to mention gas which is not to be fooled with!