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My Boiler Keeps Losing Water Pressure – Help!

Does your boiler or central heating keep losing water pressure? Here’s a handy guide to help you try to resolve the problem yourself, with your own boiler.


Does your boiler or central heating have a problem with losing pressure?


  • Is your boiler constantly losing pressure? Weekly, daily or even hourly?Dont panic
  • Is your boiler making strange, worrying or frightening noises?
  • Does the boiler keep giving you fault codes to re-pressurise the system?
  • Does the “low pressure” light keep coming on?
  • Is the heating not getting up to the temperature you set?
  • Is the central heating or hot water (or both) not working as they should be?
  • Does the pressure keep rising, then drops to nothing?
  • Does your pressure gauge keep going down?
  • Do you have to keep resetting your boiler when the pressure drops?


Please try to not worry too much about this problem – if you attempt to resolve your boilers’ pressure loss yourself and find that you need expert help instead, it can be resolved by an AHP Boiler Services gas-safe registered heating engineer. We’re only a phone call away.


Boiler or Central Heating Pressure Loss
– 3 Problems and Remedies


#1 - Boiler Re-Pressurisation


  • Find your “fill valve”, then re-pressurise your boiler system to 1 Bar - this should get your system up and running again. Check the boiler manufacturer's instruction manual, left with your boiler (or look online). This should give full instruction on how to refill the system.
  • If you can’t find or locate your boiler manual, contact us. We’ll be more than happy to assist either over the phone or via appointment with a service engineer.
  • Important note: it’s bad for the boiler if you keep replacing the water. This could lead to other parts of the boiler needing to be replaced.


#2 - Check for leaks around the central heating system


  • Check all radiator valves for leaks - just a small drip can make your boiler lose pressure over the course of a few hours
  • Check the boiler underneath for any signs of water leaking


#3 – Check the safety discharge pipe


  • Check the safety discharge pipe work for leaking OUTSIDE the property.
  • There is a safety discharge pipe that lets water out of the boiler, if there is a problem with the boiler becoming over pressurised. It will begin to drip or run with water. This is called the Pressure Relief Valve Discharge Pipe (or commonly called the “P.R.V”)
  • It’s a small pipe, which can only be seen on the outside wall of where the boiler is installed. Here’s what it might look like outside your house. Some customers refer to this as the Boilers’ Overflow Pipe:


Safety Discharge Pipe


  • If your pressure relief valve is leaking, it could mean that you have one (or more) of the following problems.

Problem: Your Pressure Relief Valve needs replacing - it’s become weak on holding back the pressure.
Remedy: Install a replacement P.R.V.

Problem: Too much pressure has been put into the system. You could have a pressure gauge that’s not giving a correct pressure reading and now, due to over-pressurisation, the pressure relief valve (P.R.V) is faulty and needs replacing.
Remedy: Install a replacement P.R.V and possibly a new Pressure Gauge.

Problem: A faulty filling valve is not shutting off correctly, so the water pressure is getting too high in the boiler.
Remedy: Install a new Filling Loop or Filling Valve.

Problem: There’s oxide sludge in the system which has damaged the Pressure Relief Valve (P.R.V.)
Remedy: Power Flush the central heating system and install a new P.R.V.

Problem: If the expansion vessel, which allows the system’s water to expand, is faulty, the pressure will rise dramatically when the boiler is running. The P.R.V. will then automatically keep dumping the water in the system to the outside.
Remedy: Install a new Expansion Vessel and a new P.R.V.

If you’re unable to resolve the low water pressure problem(s) with your boiler, don’t despair! AHP Boiler Services have skilled gas-safe engineers that can be with you the same day to give you a no-obligation quotation to repair these problems, with a guarantee on all works.

Book your appointment by contacting us today. Alternatively, find out more about us, take a look at our Google+ reviews or read our customer testimonials.

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