Boiler Losing Pressure - Here's Why!

A boiler losing pressure will stop your central heating from working and leave your home without hot water.

  • What Boiler pressure is
  • What pressure your boiler should be set to
  • The common signs of low boiler pressure
  • Water leaks as a  cause of pressure loss
  • Faulty boilers causing pressure loss
  • How to top up boiler pressure
  • What to do if the boiler pressure keeps dropping

What Is Boiler Pressure?

Boiler pressure is the pressure of the hot water inside your central heating system.

The boiler has a pressure sensor which measures the water pressure in your central heating system.

The pressure of your heating system is displayed on the boilers pressure gauge.

What Pressure Should Your Boiler Be

What is the correct boiler pressure?

When the central heating system is cold the boiler pressure should be between 1 and 1.5 bar. The pressure gauge can increase to 2 bar when the heating is hot. If the pressure in your central heating system is too low your boiler will cut out. If the pressure is too high it may damage boiler components or cause your heating to leak.

What are the signs of low boiler pressure?

There are 7 key signs to look for when you suspect your boiler is losing pressure;

  • Hot water is not working because the boiler is not switching on
  • Central heating is not working because the boiler is not switching on
  • The boiler is making strange sounds as air is in the heating system
  • Central heating pipes creak, groan and knock with vibration from a water hammer
  • Radiators not warming up properly due to air in the system
  • Boiler gauge is showing boiler pressure of less than 1 bar
  • Boiler displays a fault code indicating low boiler pressure

Low Boiler Pressure Fault Codes

Boiler ManufacturerLow Boiler Pressure Fault / Error Codes
Worcester Bosch1017 W
Alpha BoilersFault Code 10
Ideal BoilersF1, FD, Water Pressure
ViessmannPressure gauge reading lower than 1 bar
VaillantF.22 / F.75

Can a boiler lose pressure due to a water leak?

A boiler can lose pressure due to a water leak.

Water leaks from boiler components, pipes or radiators reduce pressure inside the central heating system.

This loss of pressure is represented by an error code and/or low reading on the boiler’s pressure gauge.

Our central heating leak detection specialists can help if your boiler is losing pressure.

Can a boiler lose pressure because of a fault with the boiler?

A boiler can lose pressure due to its own internal faults.

A malfunctioning pressure relief valve or a compromised heat exchanger can cause pressure drops. 

These faults disrupt the boiler’s ability to maintain optimal pressure, indicated by a declining gauge reading.

How To Repressurise A Boiler That Is Losing Pressure

Follow these step by step instructions on how to repressurise your boiler yourself:

  1. Switch off the boiler at the thermostat and allow it to cool – this is perhaps the most important stage, and should not be skipped or rushed
  2. Double check the boiler to ensure that both ends of the filling loop are securely attached, and in good condition.
  3. Open both of the valves SLOWLY – using a screwdriver. This allows the cold mains water to enter the system, and should be audible if you listen closely.
  4. Watch the pressure gauge; when it hits the 1.5 bar, you are good to go.
  5. When the dial hits 1.5, close both valves
  6. Switch the boiler back on, and hit the reset button

What to do if the boiler looses pressure again?

Repetitive re-pressurizing of your boiler shouldn’t be ignored. Constantly needing to refill your boiler is a strong signal of a water leak.

Here at ADI Leak Detection, our team is highly skilled and qualified in detecting and repairing water leaks. 

Our experienced team are Central Heating Leak Detection Specialists, have the equipment and knowledge to trace a leak on your heating system causing your boiler pressure loss.

Leak Detection Company For Low Boiler Pressure

Our Reviews & Accreditation’s

CIPHE - Chartered Institute of Plumbing and Heating Engineering

ADI Leak Detection is accredited with The Chartered Institute of Plumbing and Heating Engineering.

ADI Leak Detection is registered with The Water Industry Approved Plumbers’ Scheme.

ADI Leak Detection is registered with The Water Industry Approved Plumbers’ Scheme.

ADI Leak Detection is a Watersafe Accredited contractor.

Adrian Morgan

Adrian Morgan CIPHE RP RHP is the founder & Managing Director of ADI Pro Leak Ltd. Adrian is also the Head Plumbing, Heating & Leak Detection engineer at ADI Leak Detection.

Adrian CIPHE RP RHP is proud to be registered with the Chartered Institute of Plumbing & Heating Engineering, a Registered Plumber and a Registered Heating Professional.