How to Increase Boiler System Pressure


The boiler is a critical element in our homes. Most of us will know the term ‘low pressure’, but what does it mean?

If you’re experiencing problems with your boiler – namely a loss of heating and hot water supply – low pressure could be at fault. 

If the pressure in your boiler is lower than usual, our useful guide can tell you why this happens.

We’ll also show you how to make simple checks to help diagnose a problem, plus we’ve tips on how to top up your boiler pressure. 

What is Low Boiler Pressure?

Water that flows around the pipes and radiators in our homes is heated by the boiler.

To work as efficiently and consistently as possible, the pressure in the boiler system needs to remain stable. If the pressure in your boiler drops beyond its optimal level, it can’t sufficiently heat the water – leaving you without heating or hot water.

As you might imagine, the pressure requirements for boiler types are different. To quickly and easily find out exactly what your boiler pressure should be, start by checking the manufacturer’s handbook or manual.

Here, you’ll find the correct pressure information and accurate measurement details for your boiler.

What Causes Low Pressure on a Boiler

With so much happening inside your boiler, it isn’t surprising that the pressure of your boiler can vary. It’s important to understand why the pressure in your boiler can drop.

If the reading you see on the pressure gauge is too low, it could result from one of these common causes:

1. Water Leak 

A leak is common on a pressurised system, and even the smallest weep from a pipe or radiator valve can cause issues for your boiler.

While you can’t check a leak inside your boiler system (it’s best to leave that to a professional), checking for leaks around pipes and radiators – including the joints and bends of the pipes that are visible is easy.

Look for damp water patches on or around floorboards, carpets, ceilings and around the exterior of the boiler itself. 

While an internal boiler leak over time could lead to a gradual drop in pressure, it’s important you don’t attempt to look for leaks inside the boiler yourself. A Gas Safe registered engineer is trained to deal with internal boiler leaks. 

A faulty boiler part is not something you should fix yourself. If you’re unsure of what to do, contact Blue Emergency Cover, who can diagnose the problem efficiently.

2. Radiator Bleeding/ Venting

If you’ve recently bled one or more of your radiators, this can cause pressure in the system to decrease.

By bleeding a radiator, air trapped in the system is released. For the pressure to rise again, the air must be replaced by water.

How Can I Check My Boiler Pressure?

Here are some quick and easy checks you can do, to find out if your boiler pressure is correct or running low.

You’ll find a pressure gauge on the front panel or underneath the boiler (a green to red indicator display).

Most conventional boilers either have a digital display with numbers in bars or a round gauge with a needle on a dial pointing to the pressure level.

If your boiler is older, the pressure gauge can usually be found underneath the boiler.

Pressure typically sits between 1 – 1.5. Anything below this could indicate loss of pressure, through a leak or following a radiator bleed.

A switched off cold boiler should sit at around the number 1 on the gauge.

The pressure is too low if:

  • The pressure gauge reads below one (one bar), or the needle has moved to below 1.
  • A flashing error message or reading appears on the LCD display.

Check your boiler’s instruction manual for further information if you’re unsure, or contact Blue Emergency Cover to book an engineer to keep your boiler running efficiently.

How to Fix Low Pressure

There are some simple steps you can take to correct the pressure yourself.

If the pressure reading is below 1.5, this could indicate that the boiler needs to be re-pressurised.

This is an easy job that keeps your boiler working efficiently. If you’ve already checked the pipes, radiators, radiator valves and around the boiler itself and haven’t discovered any leaks, you can top up the system by adding more water.

If this doesn’t work, follow these steps:

  1. Locate the boiler manual and find the pages on low pressure/filling boiler.
  2. Switch your boiler off and wait for the system to cool down (at least an hour).
  3. Check both ends of the filling loop are securely attached (your boiler may use a key instead).
  4. Open both valves to let water into the system (listen for the sound of running water).
  5. Check the pressure gauge has risen to 1.5.
  6. Close both valves tightly, one at a time.
  7. Turn the boiler back on (you may need to push the reset button).
  8. Undo both ends of the filling loop – catch any excess or dripping water with a towel.
  9. Store the filling loop (or key) somewhere safe.

Still Need to Increase Boiler Pressure

If you’re still struggling to regulate the pressure of your boiler or are unable to locate the filling loop or filling key, you may want to think about getting your boiler re-pressurised by a specialist.

If you’re unable to identify both the cause of the issue and how to fix it, get in touch with Blue Emergency Cover. As expert technicians, we can help. 

Did you know, that we offer unlimited repairs to Blue Emergency Cover plan customers? If you need affordable boiler cover, we offer immediate protection – helping you avoid any unexpected repair costs. Why not call us today and speak to our team.