Why does my hot water run out so quickly?

There's nothing worse than a shower going cold halfway through the shampoo. When a hot water system that used to last suddenly runs out fast, it's telling you something has changed inside the tank. Terry has traced this exact complaint hundreds of times across Auburn, Regents Park and Bankstown, and it nearly always comes down to one of a handful of causes.

The usual suspects in an electric tank

Most electric storage tanks have two heating elements, an upper and a lower, each paired with its own thermostat. The lower element does the bulk of the work. When it fails, the top third of the tank still heats through the upper element, so you get some hot water, but it runs out quickly and what's left arrives lukewarm.

• A failed lower element: you get a short burst of hot, then a fast fade to cold. That's the classic sign the bottom element has died.
• A faulty thermostat: a thermostat that's stuck or reading wrong won't heat the tank to the right temperature, so there's less usable hot water to start with.

Both are common on tanks past the 10 to 12 year mark, and both are a licensed job because the elements are hard-wired. This is not one to open up yourself.

Sediment: the slow thief of tank space

Over the years, minerals and grit settle to the bottom of the tank. That layer takes up volume that used to hold hot water, so a 250 litre tank can effectively hold a good deal less. Sediment also insulates the lower element from the water, making it work harder and fail sooner. If your tank rumbles or crackles while heating, that's sediment, and it often shows up as both a noise and a shrinking hot water supply. A flush can recover some of that lost space.

A broken dip tube, or a thermostat set low

The dip tube carries incoming cold water down to the bottom of the tank so it heats before rising to the outlet at the top. If that tube cracks or breaks, cold water dumps in near the top and mixes straight into your hot outlet, turning the water tepid fast. It's less common, but Terry does see it. Simpler still, the thermostat might just be set too low. Storage tanks are usually set around 60°C at the tank for safety and to kill bacteria, with a tempering valve bringing bathroom water down to 50°C. If someone has wound the thermostat right down, you'll get less hot water than the tank is capable of.

When the system is just too small

Sometimes nothing is broken. If the household has grown, added a bathroom, or swapped to bigger rain showerheads, an older tank might simply be undersized. As a rough guide, 125 to 170 litres suits 1 to 2 people, 250 to 315 litres suits 3 to 4, and 315 to 400 litres suits 5 or more. If you've outgrown the tank, a larger storage unit, or a switch to gas continuous flow that never runs out, is worth a look. Terry will tell you honestly whether a repair or a replacement makes more sense for your place, rather than pushing a new unit you don't need.

If your hot water is running out before everyone's had a shower, call Terry on 0415 274 542. He services all the main brands across Western Sydney and quotes a fixed price up front.