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Why don’t I have hot water?

Having no hot water is a problem no one wants to have. Our experts are here to break down the most common boiler issues that can result in no hot water being produced in your home.

What causes hot water to stop working?

Hot water problems can occur for many reasons, but most typically stem from a boiler fault. If your boiler is faulty, a fault code will display on the screen. Checking the code in your manual can help you to identify the problem yourself.

To find out what your boiler fault code means, check out our fault code guide here.

For most boiler problems, it is advised that you should contact you local installer to fix the issue.

Water Pressure

Making sure you have the correct boiler pressure is essential to a working heating system. If water pressure gets too low, or too high, the system will automatically switch off, resulting in no hot water in your home.

Optimum boiler pressure should sit between 1 and 2 bars. A boiler error associated with a water pressure issue will result in your Glow-worm boiler screening the F7 fault code.

Signs of water pressure issues: (icon variation)

  • Pressure falls below 1 bar.
  • Pressure goes above 2 bars.

Boiler pressure issues are often be an easy fix, learn more about managing boiler pressure here.


Issues with your pipes could also be the cause of you having no hot water in your home.

Signs there is a problem with the pipes include:

  • Frozen pipes – cold weather can freeze your boiler’s external condensate pipe. The condensate pipe is usually located on the nearest outside wall to your boiler.
  • Airlocked pipes - air gets trapped in the pipes and leads to blockages.

Issues in the pipes can be tricky to identify and you shouldn’t touch the pipes yourself. The codes F1, F4, F28, and F29 will appear on your Glow-worm boiler if there is a pipe issue.

If the issue is a frozen pipe, you can try to thaw it out using hot (not boiling) water. Find out how to defrost your frozen pipes here.

Diverter Valve

Another common cause of hot water issues can be down to the diverter valve if you have a combi boiler. A diverter valve is a mechanism that lets hot water in and out of your system, as well as your radiators, taps and shower.

Common signs the hot water issue is director valve related include:

  • Lukewarm water coming out of taps.
  • Hot water only switches on when central heating is on.

If you have a diverter valve issue, it is best to contact one of our specialist installers.

Other Causes

If the above reasons don’t seem to be the cause of your lack of hot water, it could be due to other issues. These may include:

Usually, in old gas boilers, the pilot light is the flame that is always present in the gas system. However, even if the flame goes out, the gas supply doesn’t stop, so it is important to get in touch with your installer immediately.

When boilers detect an issue, they tend to shut down. You will need to contact your installer to help solve this issue.

A fault in the thermostat will impact the signal between itself and the boiler which will ultimately cause no hot water.

Still got no hot water?

If you’ve still not got any hot water in your home, contact our Glow-worm team of expert installers who will be happy to help.