Well, there are only two major appliances in the house that we hadn't replaced since moving in - the furnace / AC and the water heater. And now, there's just one. The water heater started leaking and set off the flood detector Friday morning. We called our favorite plumber (Gus at Castle Plumbing), and he said he could come out and take a look Saturday, but that if it needed to be replaced and we couldn't wait until Monday that that likely meant getting a new water heater at Home Depot, since nothing else would be open. But the good news is that the Home Depot water heaters are made by Rheem, which has a good track record.
In the meantime, we called a national plumbing chain (I won't mention their name) and they sent someone out who gave us a free estimate of $1300, but who knows whether they would have put a good water heater in for that price? In any event, that's way, way too much, so they were dismissed.
Saturday came around and I decided that it was just too likely that the water heater had to be replaced. It was 11 years old, and I strongly suspected that it wasn't the 12 year warranty kind. One thing you can take to the bank is that an N year warranty water heater will last for about N years + 1 day before giving out. So I decided to attempt to save some money by at least starting the demolition of the old unit myself. It was pretty easy, and I managed to get the old unit out all by myself. The gas and water connections came off with a wrench. The T&P relief valve had a sweated connection that I needed to desolder before I could unscrew the rest of it. Lastly, the chimney was held on with a couple of sheet metal screws.
We went to Home Depot and bought a 12 year warranty 40 gallon natural gas heater. It was about $550 or so, but the extra-cheap 6 year warranty units were about $400, so I think that's pretty clearly money well spent.
In retrospect, I probably could have installed the new unit myself. The new unit is a little taller than the old one was, because between then and now the building code has an added safety requirement - a special sealed combustion chamber that has a spring-loaded door held open by a thermal fuse. The idea is that if the burner area overheats, the door will spring shut cutting off the combustion air flow, choking off the fire. I had Gus install the new water heater mostly because of the fear that the size difference was going to make a difference between it being easy and being hard. The worry was that the water connections were going to need to be moved, which would have involved tearing out some sheetrock in the back of the water heater alcove. But there are flexible copper pipes and there was enough flex left for the new heater to fit. The only other work needed was to trim the chimney to fit and to re-plumb the T&P relief piping.
The last advice Gus had was to keep the home depot receipt, because Home Depot has a reputation for doing anything they can to low-ball you on any warranty claims. I stapled it to the door of the water heater closet. He also said we should drain it once a year, but that didn't mean emptying it all the way - just opening the drain valve and pouring off a gallon or two is enough.