Ideal boiler F1 fault: what causes it & how to fix it

The Ideal boiler F1 fault means that the water pressure in your system is too low for your Ideal boiler to operate. You can easily fix this problem by topping up the pressure yourself.

Ideal boiler F1 fault explained

In a combi boiler heating system, the water pressure must be at least 1 – 1.5 bar when cold. Any lower than this, and the boiler simply won’t come on.

Depending on which model of boiler you have, you may see that some of the numbers on the pressure gauge 1, 1.5 or 2 are tipped with green. The pressure should be in this range when the system is off.

You can top up the water pressure yourself by opening the filling loop until the pressure is at the right level again. The filling loop is a temporary connection to the mains, which is where a combi boiler heating system gets its pressurised water supply from.

Ideal boiler F1 fault code – how to fix

  • Turn your central heating and hot water off via the relevant control dial.
  • Look under the boiler for two blue plastic levers.
  • Turn the one on the left a quarter turn. This will open one side of the filling loop.
  • While keeping an eye on the pressure gauge, slowly turn the blue lever on the right. You should now hear a hissing, rushing sound. Do not open the lever fully.
  • Continue to keep an eye on the pressure gauge as the needle slowly rises. Once it reaches the 1 – 1.5 bar area, close the lever.
  • Close the blue lever on the left.

Congratulations – the F1 fault code should disappear. Turn the central heating and hot water back on via the control dial, and the boiler should operate normally.

I keep getting an F1 fault

On a combi boiler heating system, it’s quite normal to have to top up the pressure every few months. However, if you have to do it several times per month or week, then it’s quite possible there is a leak somewhere in your heating system or in the boiler itself. In this case, it’s definitely worth contacting a heating engineer about this problem. Constantly reintroducing oxygen-rich, mains water into your heating system will make it more prone to corrosion and the build-up of sludge inside it, making it less effective and less efficient.