Key takeaways
- Rusty water from the hot side only points to the tank. Rust on both hot and cold points to the pipes.
- Rumbling and popping are usually sediment, which is common with hard water.
- Water at the base of the tank usually means the tank has failed and needs replacing.
- Lukewarm or short-lived hot water is often a failed element, thermostat or burner part, and may be repairable.
- Plan a replacement before a heater past its typical lifespan fails on its own schedule.
Rusty or discolored hot water
Run a cold tap and a hot tap in the same sink. If the cold water is clear and the hot water is brown or rust-colored, the tank is the likely source. It may mean the anode rod is used up and the inside of the tank has started to corrode. A rotten-egg smell in the hot water only usually points to bacteria reacting inside the tank, and a plumber can check the rod and the tank.
If both hot and cold run discolored, the heater is probably not the cause. Older homes in the region can still have galvanized or cast iron piping, and rust that shows up first thing in the morning or after the house has been empty can come from those pipes. A water main repair in your neighborhood can also stir up discolored water for a short time.
Rust in the hot water does not always mean the heater is about to fail, but combined with age it deserves a plumber's look.
Rumbling, popping and banging
A rumble or pop while the heater is heating is usually sediment. Hard water leaves mineral scale that settles on the bottom of the tank, and water trapped under that layer boils and bursts through it. The heater works harder, the bottom of the steel gets hotter, and the tank wears faster.
A flush can quiet the noise if the sediment is still loose. The flushing guide explains how it is done. If the sediment has hardened into a crust, flushing will not remove it and the noise comes back.
Banging in the pipes when a faucet or appliance shuts off is a different problem. That is water hammer, caused by fast-closing valves, loose pipes or high water pressure. It is not a sign the heater is failing, though a plumber can check your pressure and add arrestors if needed.
Leaks at the base and elsewhere
Where the water is coming from matters. Water at the top of the heater often comes from the supply connections or from the relief valve discharge pipe, and those can sometimes be repaired. A drain valve that seeps can often be fixed too. Water pooling at the base that comes from the tank itself usually means the steel has corroded through. A tank cannot be patched, and the leak can get worse quickly.
Condensation can look like a leak. On a cool basement floor in summer, moisture can form on cold pipes or on some high-efficiency units, so check whether the water is actually dripping from the tank.
If you find a leak, shut off the power at the breaker for an electric heater, or set the gas control to off for a gas heater. Close the cold water supply valve above the tank. Then call a plumber. If the water is near outlets or the panel, stay out of it. Our leak repair service covers heater leaks and the damage they can cause, and you can contact us to arrange a visit.
Inconsistent temperature and running out of hot water
Hot water that turns lukewarm, swings between hot and cold, or runs out faster than it used to has several possible causes. In an electric heater, a failed element or thermostat is common. Because the upper element heats the top of the tank first, a bad lower element can leave you with a short supply of hot water. In a gas heater, a worn thermocouple, a clogged burner or a failing gas control can cause weak or uneven heating.
Sediment also takes up space in the tank, so there is less room for hot water. A cracked dip tube sends cold water to the top of the tank where it mixes with the hot, which makes the water lukewarm.
If only one fixture has the problem, the heater may not be the cause. A worn faucet cartridge or mixing valve can do the same thing.
Parts like elements and thermostats are often worth repairing in a heater that is otherwise sound. If a gas pilot keeps going out, the flame looks yellow or flickers, or you see soot around the heater, shut it off and call a plumber. Those can be signs of poor combustion or venting, and carbon monoxide is a real risk.
Age and what to do next
Most tank water heaters last somewhere in the range of 8 to 12 years, though some last longer. The age is on the data plate on the side of the tank. The serial number usually encodes the manufacture date, but each maker uses its own format, so a plumber can read it for you.
If your heater is past ten years old and shows any of the signs above, plan a replacement instead of waiting for it to fail. A planned replacement lets you choose the right type and size. An emergency replacement happens on a weekend, with water on the basement floor and few options.
The tank vs. tankless guide can help you decide what to put in next. When you are ready, our water heater service page explains what we handle.
Frequently asked questions
Is a little water dripping from the relief valve pipe normal?
A small amount of occasional dripping can happen when pressure rises as water heats, but steady dripping is not normal. It can point to high water pressure, a thermal expansion problem or a worn valve. Do not cap the pipe, and have a plumber check it.
How long can I wait once the tank is leaking?
If the water is coming from the tank body, you should not wait. Shut off the power or gas and the cold supply, drain what you can safely, and call a plumber. The leak can grow without warning and damage floors and belongings.
Does rust in the hot water always mean I need a new heater?
No. Rust in both hot and cold water points to the pipes, not the heater. Rust in the hot water only is a warning sign, especially with an older tank, but a plumber can check the anode rod and tank before you decide.
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