Hopefully someone can benefit from my experiences.
2 1/2 years ago I installed a brand new water heater in a rental. It was made by Whirlpool, and purchased at Lowes. One year later, one week out of warranty, the thermocouple went bad. I went to Lowes to get a replacement, and the guy there said "we sure sell a lot of these". Words to remember.
Last week I got another call that the water heater didn't work again. At the time I was on my way to the WW show, so I called a handyman I use occasionally. He spent 4 hours working on it, installed another thermocouple, and still couldn't get it to stay lit. $266.14 down the drain.
Next day I skipped the WW show, bought a new water heater (GE from HD), and spent about 4 hours installing it. Back in business. Total cost to get hot water back was about $800 that I shouldn't have had to spend for another 8-10 years.
The problem: Poor design on the part of Whirlpool. If you go to Lowes and look under the Whirlpool, you will see that all the air for combustion has to enter from the bottom of the heater through a small panel of tiny louvers. So small you can't even slide a FLAT toothpick through them. These get clogged with dust and lint, overheating the unit till something gives. The panel is almost inaccessible for cleaning, and in my installation with a drip pan under the heater it is ablsolutely impossible.
Now go to HD and look at where the GE unit draws in air. Many, much larger holes around the sides of the unit at the bottom. Easily accessible for cleaning, and much, much less likely to clog up anyway.
Hope this saves someone the time and money I wasted.
Rick Potter