0333 344 8968

← Back to blog

First, what is boiler pressure all about anyway?

Well, boiler pressure refers to the pressure of hot water running in your sealed central heating system, and boiler pressure can fluctuate for different reasons.

When your boiler begins to heat water, the heated water expands and causes the pressure gauge to show an increased reading.

This is nothing to worry about, especially when you’re both using the central heating and running hot water. Boilers have what’s called an expansion vessel which is able to accommodate these sudden leaps in pressure.

What pressure should your boiler be at?

Your boiler’s pressure is displayed on the built-in pressure gauge, and should read around the 1 bar mark when you’re not running any hot water and the heating isn’t turned on. Therefore, 1 bar is a low-pressure setting.

When the heating is turned on, your boiler pressure should be between 1.5 and 2 bars. Most boilers will highlight this area in green on the pressure gauge, clearly showing you that the pressure setting is correct.

So, what if your boiler pressure reading is too high?

If you discover that your boiler pressure is too high, here’s how to reduce it yourself and return the pressure to its correct setting.

Follow these six steps to help lower your high boiler pressure:

  • Switch off your boiler and wait for the heating system to cool.
  • Check the boiler pressure gauge and if it’s above 2 bars, you’ll need to reduce the pressure.
  • Make sure the filling loop or relief valve is tightly closed.
  • Bleed your radiators to release trapped air from the heating system.
  • Check to see if the boiler pressure has returned to its correct setting. (Around the 1 bar mark when you’re not running any hot water and the heating isn’t turned on; between 1.5 and 2 bars when the heating is turned on.)

What if your boiler pressure is still too high?

In this case there could be one of two reasons:

  1. Your expansion vessel needs repressurising.
  2. There’s a fault with the filling loop. (A hose used to repressurise your boiler and top up the water when you drain or bleed your system.)

Unfortunately these are not jobs you can safely do yourself, and will need to call a Gas Safe registered engineer to fix for you.