Signs your water heater is about to fail (and what to do about each one)

The usual signs that a water heater is failing are water that no longer gets hot enough, rumbling or banging noises, rusty or cloudy hot water, and moisture or a puddle around the tank. Most of these have a cause a technician can fix, and some are urgent. If you smell gas, see water spreading or notice scorch marks, stop using the appliance and get help straight away. Never open the burner, the electrical compartment or the gas connections yourself: that is a job for a licensed professional.

1. The water is not as hot as it used to be

A water heater that takes longer to heat, runs out quickly or gives only lukewarm water is telling you something. Common causes include sediment built up in the tank, a worn heating element or thermostat (electric models), a dirty burner or pilot (gas models), or simply a tank too small for the household. What you can do: check that the thermostat dial has not been moved, that the breaker or the gas supply is on, and whether the problem affects only one tap (then it is the tap or the pipe, not the heater). If none of that explains it, book a service.

2. Rumbling, popping or banging noises

When sediment settles at the bottom of a tank, water gets trapped underneath and boils, causing a rumbling or popping sound. It is a sign of buildup that makes the heater work harder. A technician can flush the tank, depending on the model. If the noise is new and loud, do not ignore it.

3. Rusty, brown or cloudy hot water

Check whether the rusty colour comes only from the hot tap. If cold water is clear and hot water is not, the tank or an internal part may be corroding. Rusty water by itself is not always an emergency, but it is a reason to call a technician soon, because corrosion eventually leads to leaks.

4. Moisture, drips or a puddle

This is the sign you should not leave for later. Look at the base of the tank, the pipe connections and any relief valve outlet. Wipe everything dry and check again after a day. If you find new moisture, close the water supply to the heater, switch off the power or gas supply following the manual and call a technician. A tank that leaks is rarely repairable and can cause serious water damage; see our guide to preventing water damage.

5. Pilot flame problems, soot or a smell of gas

On gas models, a flame that keeps going out, a yellow or orange flame instead of blue, or soot marks around the unit need a professional. If you smell gas, do not touch switches or lighters, open the windows, leave the home and call the gas emergency number or the supplier from outside. Nothing on this list is worth risking.

6. Age and missing maintenance

Age alone does not mean a heater has to be replaced, and lifespan depends on the model, the water quality and how the unit is maintained. The manual and the label usually give the year of manufacture, which is helpful when you speak to a technician. If your unit is old and has had several of the problems above, ask for an opinion on whether repair or replacement makes more sense.

What you can do to keep it going

• Service it once a year with a qualified technician. The water heater maintenance page explains what is usually checked.
• Look at it regularly: a quick glance at the base, the connections and the flame takes seconds.
• Do not block the ventilation around gas models, and do not store flammable things near them.
• Keep records: when it was installed, when it was last serviced and what was done. They help every future repair.
• If you rent, tell the landlord in writing when you notice a problem. Who pays depends on your lease and country; our guide to renting covers the usual split.

Never let the date slip

The annual service is the kind of task that is postponed until the hot water disappears in the middle of winter. HouseKiper reminds you every year, together with the rest of the autumn jobs: see the fall home maintenance checklist and the complete checklist.

How do I know if my water heater needs replacing?

Repeated lack of hot water, rusty water from the hot tap, noises that keep returning, an old unit and any leak from the tank itself are all signs. A technician can tell you whether a repair is worth it.

Why is my water heater making a rumbling noise?

Usually sediment at the bottom of the tank. A technician can check it and flush the tank where the model allows. Do not leave it for long.

Is a leaking water heater dangerous?

It can be, because of water damage and, in electric models, contact with electrical parts. Close the water supply, switch off the power or gas and call a technician. Do not touch the electrical parts.

How often should a water heater be serviced?

Once a year is the usual recommendation in the catalogue of HouseKiper, but check your manual and the installer's advice for your model.