Your water heater is trying to tell you something

A tank water heater is a steel drum holding forty or fifty gallons of hot water, and its life is a race between the anode rod inside it and the water. When the anode is gone, the tank rusts from the inside, and one day it lets go. The average tank lasts eight to twelve years. Nobody gets a warning letter; the warning is on the floor of the utility room.

Here are the signs, the two jobs that push the date back, and how to think about the replacement.

Four signs

• Rumbling or popping when it heats. That is sediment on the bottom of the tank boiling water trapped under it. The sediment insulates the burner from the water, so the heater works harder and the bottom of the tank overheats.
• Rusty or discolored hot water, but clear cold water. The tank is rusting inside. Once you see this, the leak is months away, not years.
• Water around the base. Look under the tank with a flashlight. A drip at the relief valve or a fitting can be fixed; moisture from the seam of the tank itself cannot.
• Age. Find the manufacture date on the label; it is usually encoded in the serial number and the maker's website decodes it. Past ten years, plan for it. Past twelve, it is living on luck.

Two jobs that add years

Flush it once a year. Turn the heater off, connect a hose to the drain valve at the bottom, open a hot faucet upstairs to let air in, and drain until the water runs clear. On a tank that has never been flushed the first bucket will be startling.

Check the anode rod every three years. It is a magnesium or aluminum rod that screws into the top of the tank and sacrifices itself to the water so the steel does not have to. When it is down to the bare wire, a new one is thirty dollars and an hour, and it can double the life of the tank. A plumber does both jobs in one visit if the rod is seized, which on an older heater it usually is.

The relief valve

The temperature and pressure relief valve on the side or top is the safety device. Lift the lever once a year and let it snap back; you should get a burst of water into the drain tube. If nothing comes out, or it does not stop dripping afterwards, replace it. A heater with a stuck relief valve is a pressure vessel with no release.

Thinking about the replacement

If you are replacing before the failure, you have choices. A heat pump water heater uses about a third of the electricity of a standard electric tank and is worth the extra cost in most climates, especially with the tax credits that apply. A tankless gas unit gives endless hot water in a small box but needs a larger gas line and yearly descaling. A like-for-like tank is the fastest and least expensive.

If you are replacing after the failure, you get whatever the plumber has on the truck. That is the real argument for watching the date.

One more thing

Put a pan under the tank with a drain line, or a leak alarm on the floor beside it. Both cost less than lunch. The water heater will leak one day, and the difference between a puddle and a flood is whether anyone is told.