I had to replace a 9 year old gas water heater yesterday in my house. The old one had rusted and leaked.
Apparently, the expected life for a residential water heater is about 10 years.
Why are these not made of some composite material that doesn’t rust or corrode? I can understand that the gas ones may need to be fabricated from some kind of metal because gas flame is used to heat the water but electric units could be fiberglass no?
And other than draining the thing twice a year, is there anything I can do to stop my new one rusting through in 7-10 years?
This is very important:
Avoid exposing it to moisture.
You could always go for one of the new tankless models. They’re more efficient but they require (at least) two 240-volt circuits and they’re noisy. There’s no big metal tank to drain or slowly rust out.
The last time ours broke, the repairman told me that there was a company that made stainless steel ones back in the 50’s that never corroded, and then went out of business.
I don’t know if that’s just urban legend or not, though. It’s certainly something people like to say.
10 years is about what you’ll get with no maintenance. As others have noted, you should be able to do substantially better if you keep ahead of corrosion by monitoring the anode and replacing it when necessary. How often you’ll need to do this will depend on the quality of your water and the rate at which you use it.
The obvious problem is that things like fiberglass are thermal insulators. Not exactly a smart thing to make your tank out of if you are trying to heat it through an external flame.
I had a plumber come to the house once to estimate some work. This is what he told me about hot water heaters, although I can’t verify.
With HWHs, in addition to different capacities, you can get varying warranties (from say 10 years to 20 years). There is no appreciable difference between them in terms of longevity (there may be additional features), so you are in effect paying for an insurance policy. In addition, the hotter you heat the water, the faster it corrodes. His suggestion for a large family that goes through a lot of water was to buy two HWHs (say two 30 gallons) and to hook them up in series. The first would be the shorter warranty and preheat to a very low temperature, theoretically lasting a very long time. The second would bring the water to the final temperature, and should have the extended warranty. Never tried it, so I can’t say whether it was a good idea or not, but it sounds reasonable to this layman, although a bit costly at the beginning. It was just my wife and I at the time, and we weren’t looking for a large capacity, so this just seemed to be wasteful for those with small hot water needs. I just plan on the replacement as one of those things that goes with home ownership.
At one time, water heaters were made of copper. As well as non-corroding, copper has a much better thermal conductivity than steel. Do any mfgs make water heaters with copper tanks, anymore?
This is not entirely true. While it is true that you will see three water heater that go up in price and warranty, you will also notice that the diameter increases. This is to accommodate the extra insulation that is present in the more expensive model.
Also, all water heaters with tanks that I have seen recently have a glass lined tank as seen here. So, the metal tank should not be contacting the water under normal operation.
Why would you want thermal conductivity in a water heater? You want the tank to be as insulated as possible so you are not continually heating water that is just sitting in the tank.
::: Reads thread.
Wife calls out, “No hot water.”
Rick finds pilot out. Rick relights pilot, and finds all OK.
Rick decides to drain tank since it is cool anyway.
Rick finds damn drain cock won’t shut off.
Now Rick has to drain the damn thing entirely to fix drain cock, or replace the unit.
Rick shakes fist in the air::: Damn you MrFloppy this is all your fault!
Never been a fan of electric water heaters. They are easily what, 20 per cent of the electric bill? I just gotta get a timer for that thing. I suppose a gas water heater is wasteful too, or can be. Always thought that a gas water heater provided a better shower for some reason, but hot water should be hot water.
If you have “hard” water or a lot of sediment, it will fairly rapidly calcify and substantially reduce the volume, and probably wear out much sooner. Water softeners help on this.
They use an immersible heating element similar to the coils on an electric stove, but instead of a spiral coil, the element is usually a straight, skinny arrangement that’s mounted through the side of the tank, in direct contact with the water.
There’s probably no overwhelming reason other than inertia and tradition that an electric water heater tank couldn’t be fiberglass or whatever else as it’s not a direct player in the process of making water hot. A gas- or oil-fired heater does need to be metal so the heat from the flame under the tank will be conducted to the water. Also, fiberglass or other composite material would most likely burn pretty quickly with a flame just inches away.
All I can say is from my experience. In 1962 my parents built their house. In 1977 they plumbed a wetback woodfire into it, which regularly boiled the hot water. In 1999 they sold. During all that time the same electric copper hot water cylinder was used. Our water was collected from the roof and kept in a concrete water tank.
The house they moved into has two electric hot water cylinders. The older one is from 1971, vented as their first house through a pipe above the roof to give the required head. The second cylinder is vented by an expansion valve. The second was less than 10 years old when it split this year. The plumber said the tank splits because of the flexing it takes as taps are turned off. I don’t know whether the newer cylinders are made from thinner/harder copper alloy, or the expansion valves allow a greater shock to the cylinder than the free vented style when the taps are turned off. The water in this house comes from the roof, and from a bore through a softner.
Rick relights pilot, and finds all OK. 
