The thermocouple’s function is to turn off the gas if there’s no pilot light lit. If you look closely at the burning pilot light, there is a small silver- or copper-colored metal tube that sits directly in the flame. At the other end of the tube there is a very thin piece of copper or silver colored tubing that connects from the thermocouple sensor that sits directly in the pilot flame to the main gas controller or regulator on the HWH. The thermocouple generates a small amount of electrical current when it’s been heated by the flame. This small amount of electrical current keeps the gas safety valve open. If the pilot light gets blown out or fails for some other reason, the current stops and the gas valve closes...that’s the safety function in operation: no flame, then no gas flows.

When our client attempted to re-light his pilot light, he probably held down the over-ride button for about 30 seconds. This allowed the gas to flow long enough to heat up the thermocouple and generate some electrical current flowing back to the gas valve. Then, when he released the over-ride button the gas continued to flow, as designed. However, since the burner (and pilot) eventually went out, we anticipated there was a problem with an intermittent connection in this component, such that the thermocouple ceased to provide electrical current, and thus shut down the gas flow, and ....oops, no hot water! If the thermocouple has been fully defective, then as soon as our client had released the over-ride button, since there would be no electrical current, the gas would have immediately stopped flowing and the pilot light would not stay lit except via the override. Our client’s description of his failure mode makes me fairly sure that he had a thermocouple that was intermittently operational... failing part of the time. And that’s essentially the same as one that’s totally failed, in that you don’t want an unpredictable HWH! The thermocouple is a pretty common failure on water heaters and furnaces. The good news is that the part usually isn’t expensive, but if you have to call a plumbing contractor, the service call can be >$85-$120, in addition to the parts.

If replacing the thermocouple doesn’t solve the problem, then it could be a bad gas regulator valve, although those are very rarely defective....fortunately, since they are much more expensive. In this client’s case, we just looked up his Maytag Series-10 model and determined that all series-10 models, manufactured by State Industries, have a 10-year limited warranty against tank leaks, a 5-year limited warranty against parts failure and a 1-year labor warranty. Since his HWH was over 5 years old, there was no warranty coverage he could lean on. We also determined that his model would accept a universal thermocouple replacement part, and those are easily found. (Some brands/models use a LEFT-handed thread, requiring a special part...so it’s important to check these before attempting to purchase the part of perform the repair.)

Bottom line, if your Hot Water Heater is compatible with the universal thermocouples that are widely available, then the parts cost will only be about $10-$15. For our client we picked one up at a local supply house and had it replaced within ~90 minutes.

Drain the Sludge

The next thing we asked our client was if his HWH had ever been drained. He said no. And since this HWH wasn’t one of the fangled ones (which are supposedly “self cleaning” to minimize sediment build-up in the bottom of the tank), we recommended that he drain the unit every 1.5 to 2 years. Our client was surprised that he’d never heard of the need to do this before.... A HWH that lasts 8-12 years without being drained periodically to remove the crud in the bottom might last 15-20 years if properly maintained...including being drained periodically. Draining the heater using can be accomplished very easily with a short piece of garden hose attached to the spigot located near the bottom of the unit. With our explanation of how to perform the operation, my client said he would complete the task himself.

What’s An Anode?

The last point of our discussion centered around the anode in the client’s HWH. Again, it hadn’t been checked or replaced in 5-6 years. The anode is simply a long bar of metal that’s installed so it hangs down into the tank itself, and serves as a sacrificial component. There are corrosive forces inside any HWH, and normally these would begin eating up the inside of the steel tank, eventually causing it to spring leaks prematurely. The anode draws the corrosiveness to itself, leaving the steel casing of the tank unscathed. In our client’s case, the anode was pretty seriously corroded, so we replaced it with a new one. Again, all we needed to do was source the right replacement and install it in lieu of the old one.