Five signs a water heater is about to fail

Published August 24, 2026 · Updated October 14, 2026 · Humble Services, Castle Rock

Water heaters rarely fail without notice. Early signs are easy to overlook while the hot water still works.

1. Rusty or brown hot water

Run the cold first. If cold runs clear and hot runs brown, the rust is coming from inside the tank. That is not repairable.

2. A rumble or bang when the burner fires

Sediment has built up on the bottom and the burner is heating through it. It is inefficient, it stresses the tank, and it gets worse.

3. Damp around the base

Check whether the water is coming from a fitting or the tank itself. A leaking fitting can be repaired; a leaking tank cannot.

4. Hot water running out sooner

If your showers have not changed but the hot water runs out sooner, sediment may be taking up space in the tank.

5. Age

Past ten to twelve years, the economics change. Money spent on a repair is money spent on a tank that will need replacing anyway.

Two more that people miss

The pilot keeps going out. On a gas tank, this is often a thermocouple fault that can be repaired. If you have also noticed other problems, have the tank checked as well.

Water at the relief valve. The small pipe running down the side of the tank is the pressure relief. A drip from it is usually pressure, not the tank, and often means the expansion tank has failed or was never fitted. That is worth a look before it becomes a larger problem.

What to do about it

One sign is worth watching. Two is worth a call, because a planned replacement on a weekday is a great deal less disruptive than an unplanned one on a Sunday.

Repair or replace?

A tank under about eight years old with one fault is usually worth repairing. A tank over twelve with any fault usually is not, because the next fault is close behind and the money is better spent on the new unit. Between those, it depends on what has failed and what the rest of the tank looks like. We can explain whether repair or replacement makes sense for your tank.

What we check when we come

The age from the data plate, the anode if it can be reached, the burner and flue on a gas unit, the elements on an electric one, the relief valve, the expansion tank, and whether there is water where there should not be. That takes a few minutes and tells us whether you are looking at a repair, a replacement, or nothing yet.

Maintaining an older tank

If the tank is old but not leaking, draining a few gallons from the bottom tap once a year clears some sediment and can quiet the rumble. Have the tank’s condition assessed when deciding between maintenance and replacement.