Why does my hot water run out so fast?

Has it changed suddenly, or always been like this?

This is the most useful question. If you've always run short, it's usually the size or the tariff. If you used to have plenty and now don't, something has usually failed.

If it's always been like this

The system is too small

Households grow, and a tank that suited two people won't keep up with five. Check the size on the label and compare it with our sizing guide.

An off-peak tank used during the day

Off-peak tanks heat during the tariff's set hours, often overnight. If the tank runs out in the evening, it won't reheat until the next off-peak period. A bigger tank, or a heat pump that runs on your solar during the day, can fix this.

Higher-flow showerheads

A new rain shower or high-flow head can use much more hot water per minute than the one it replaced, which empties a tank faster.

If it's changed suddenly

A failed element or thermostat (electric)

If the element or thermostat has failed, the tank may only partly heat, or heat slowly. Some larger tanks have two elements, and if one fails you'll still get some hot water, just not as much. These are repairs, not replacements, unless the tank is old.

Sediment in the tank

Sediment builds up in the bottom of storage tanks, especially on rainwater or bore water. It takes up space and can stop the tank heating properly, and you may hear rumbling or popping.

A heat pump that isn't keeping up

Heat pumps heat more slowly than an electric element, and slower again on cold mornings. If yours used to keep up and doesn't now, it may have a fault, such as a fan or refrigerant problem or a failed backup element.

A solar booster that's off

Solar systems rely on an electric or gas booster on cloudy days. If the booster's isolator or timer is off, or the booster has failed, you'll run short in winter and on overcast days.

A continuous flow unit going lukewarm

Continuous flow units don't run out, but they go lukewarm when too many outlets run at once, or when an LPG cylinder is close to empty. If it happens with one shower running, have it checked.

What you can safely check

• The size and date on the compliance label.
• Whether you're on an off-peak tariff (check your power bill).
• That the isolator switch is on and the hot water circuit hasn't tripped.
• For LPG, how full the cylinder is.

Don't adjust thermostats or open covers on electric systems. Elements and thermostats are live, and the water can be hotter than 60°C. If the checks don't explain it, see hot water repairs or call us.