I received this question from a reader recently and decided to post the answer for others. "I have turned my water heater up so that I wouldn't run out of hot water. Yet this problem still exists. Is there a water level adjustment on the hot water heater or something?"

Nope, no level adjustment. As water heaters age the calcium in the water deposits itself on the inside of the tank and the build up a thick layer of calcium inside the heater tank prevents rapid heat transfer to the water from the flame from the gas. When it is delivering water, to a shower for example, the recovery rate is slowed down considerably.

Also, the dip tube inside the heater may be rusted off and gone. That is the tube which makes the cold water going into the heater go right to the bottom of the tank instead of entering the top of the tank where hot water is exiting. This results in a mixture of hot and cold water leaving the tank and the hot water below just staying in the tank.

Electric water heaters don't suffer this problem, however the heating element can also accumulate calcium and reduce the heat transfer rate as well. Removing the heating element and soaking it in an acid solution can remove the calcium buildup and prevent failure of the element due to local overheating.

There isn't much you can do for the build-up in the gas fired water heaters except to drain them occasionally and remove any sediment from the bottom of the tank. It is rather impractical to add acid cleaners to the tank to remove the calcium so most people just live with a 5 to 10 year life of the tank.

To prevent a flood when the heater finally does leak you can set the heater inside a catch tray. Attach a drain hose to the tray and run it to a sump drain. If you really have a lot to lose by a leaking heater, like the carpet in a finished basement, place a water detecting alarm in the tray and listen for the warning bell about one month after the warranty runs out!

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