I have two 12-year old 40 gallon gas water heaters. Both of the pilot lights went out at the same time. My plumber said I needed new water heaters. My neighbor next door came over and installed two new thermocouples and now the water heaters are lit and working again. Should I expect this to happen again because of the age of the water heaters? How long do they usually last?

First there should be a reason two went out at same time, But the trouble with that age is not the little things, it is the sediment ( causing them not to heat well or be very efficient) So you will get better gas usage with a new unit.

But rusting out and leaking will be some of the main issues. Sadly the plumber did not explain things well perhaps as to it. May you get a few more years, yes of course, but after a certain point it is often better sense to replace very old units

12-15 years is very good, it should tell you on the tank what the warranty is. Thermocouples go out in a greater frequency than the tank goes bad, at least in my experience. Thank your neighbor big time, saved you a couple thousand $$

In my experience the water heaters being sold over the last 20-25 years last, on average, about 12-15 years so I'm betting you are on your last leg here.

With that being said, however, if your water heaters are in an unfinished basement then you can just wait for them to leak before replacing. Here, at a minimum, purchase a battery-operated water alarm at your local home improvement store and place it in a low spot next to the water heaters. These usually use a 9V battery and sound a 120 decibel alarm when they get wet so they are great for the money. At a maximum, they sell automatic water shutoffs that can be cut into the cold water supply and these will shut the water supply off should the included sensor sense water.

With any luck you'll get another 3-5 years out of these water heaters, but I'm betting not much more than that! When you do get new water heaters pop back here and we can discuss ANODE RODS. If you swap your anode rod out every 5 years there is almost no reason for the water heaters to fail... even 20-25 years from now... :)

Good luck!

Mark

Many thanks to those who answered my question about thermocouples and age to expect a water heater to last. So informative!