In this article, we run through 5 reasons that might cause your hot water to run out faster than usual.

We’ve all been there, tired after a long day of work, barely managing to drag ourselves to the shower. We turn on the tap, get undressed, and then stick a hand under the stream to check the water temperature. Odd, it’s tepid – so we crank the hot water tap to the max and hop in, hoping for the best. 

It gets warmer, and you start to feel the tension of the day leave your shoulders. Then, just as you let your guard down, the water turns from lovely and warm to freezing in a second, and no amount of twisting the hot tap does anything! And the worst thing is, you also forgot to leave a towel out before getting in…

Hot water running out faster than it should is never convenient, whether you’re doing the dishes, hopping in the shower, or wanting to do some laundry. That being said, the cause of your hot water not lasting as long as usual can be a bit tricky to pin down. That’s why we’ve collected 5 reasons your hot water doesn’t last long to help you identify and fix your hot water troubles.

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5 reasons your hot water doesn't last long

Old water heater

The first thing to consider when your hot water starts running out faster than usual is how old your water heater is. As water heaters age, they become less efficient and have to work harder to heat up water – which means they use more energy, and ultimately, they don’t heat water as hot or for as long as they used to. So if your water heater is getting on in years, it might be time for a hot water system replacement. Alternatively, be sure to get regular hot water system services to extend your water heater’s life!

Signs of an old water heater:

  • The water heater is more than 10 years old
  • There is corrosion in the tank
  • Discoloured hot water
  • Expensive energy bill

Faulty heating element 

A faulty heating element is another common cause of your hot water not lasting as long as it used to.

To fix a heating element, you’ll need a professional hot water system repair or hot water system replacement.

Signs of a faulty heating element include:

  • Water is not getting as hot as it used to
  • Hot water causing the circuit breaker to trip
  • Hot water not lasting as long as it used to

Sediment build-up

One of the most common causes of hot water running out faster than it used to is sediment build-up. Over time, bits of minerals and rust can build up inside your water heater, which can then clog it and cause all sorts of issues. 

The good news is that this is an easy problem to fix with a hot water system service or hot water system repair. You’ll just need to flush out your water heater to eliminate the sediment build-up. However, if the sediment build-up is particularly bad, you may need a complete hot water system replacement.

Signs of sediment build-up include:

  • Hot water heater makes strange noises
  • Fluctuating temperatures
  • The water from your taps looks rusty  
  • Higher than usual energy bill
  • Leaks near the water drain valve
  • Water takes a long time to heat up

Faulty Tempering Valves 

A tempering valve is a three-way valve in your water heater that mixes very hot water from the heater itself with cold water from the water supply and then sends the hot (but not too hot) water to the taps in your home. They maintain a steady and safe water temperature for households, usually around the 50C mark. 

A faulty tempering valve is a common cause of a household’s hot water not lasting as long as it used to, as it may mix the incorrect amounts of hot and cold water. This also means a faulty valve could cause scaldingly high water temperatures and so should be fixed immediately to avoid serious injury. 

The reason for the use of tempering valves is that water in the hot water system must be over 60C to kill bacteria, while the water in your taps can’t be over 50C due to scalding. This is detailed in the Queensland Government’s requirements for installing temperature control devices, which falls under the Plumbing and Drainage Act 2018. 

Signs of a faulty tempering valve:

  • Fluctuating water temperatures
  • Cold water
  • Low water pressure (tempering valves are also susceptible to sediment and can get clogged)
  • Hot tap dripping when not in use


Another common reason for hot water not lasting as long as it used to is leaks. If there’s a leak in your hot water system, the water will drain out faster than it can be refilled, causing you to run out of hot water sooner than usual. Leaks can also lead to higher than normal water and electricity bills.

Signs of a leak in your hot water system include:

  • Water pooling around your water heater
  • A decrease in water pressure
  • Strange noises coming from your taps or pipes
  • Your energy and/or water bill is higher than usual

Remember that regularly servicing your hot water system will help extend its functional life and avoid any unforeseen problems. To find out more, read our blog on ‘Do hot water systems need servicing?

If your hot water is running out too quickly, contact DCM Plumbing today

At DCM Plumbing we have years of experience in fixing hot water that is running out too quickly, through hot water system services, hot water system repairs, and hot water system replacements, as well as a variety of other plumbing services. We’ll quickly diagnose the problem and find the best solution for you, ensuring your hot water is running for as long as it should. Contact us today!