WHy does my boiler keep losing pressure?

Discussion in 'Screwfix' started by murrmac, Feb 26, 2013.

  1. murrmac

    murrmac Member

    My hot water and my central heating is run by a Thema Condens F30E boiler . Each evening I normally turn on the central heating around 7.00 pm for 3 hours, and the pressure is showing at 1.6.

    In the morning, the pressure is showing at .5, and I have to manually bring the pressure up by turning the two blue knobs underneath.  This is a daily occurrence. The pressure stays stable for the rest of the day, but the same thing happens again when I turn the central heating on in the evening.

    Are these symptoms indicative of a leak somewhere in the central heating system, or is there some other possibility ?

    Thanks in advance ...
  2. This is a sealed system boiler?

    (Sheesh - these enquiries should become a 'sticky'... )

    Murrmac, it's one of three (I think...) things.

    We need a wee bit more info, please - what is the pressure while the system is cold and before it's fired up? I guess that's 0.5b before you top it up - but what do you top it up to before you fire 'er up?

    What then happens as the system heats up - you say 1.6b, but does it start at this, or go up to this and does it go any higher than this when the system is piping hot?

    Do you know where your safety discharge pipe is? It will likely be on the outside wall nearest your boiler and be a 15mm copper pipe close to the ground and pointing downwards. Stick a container under this, or tie a plastic bag over it to see if any water comes out and when.

    (Likely causes - your expansion vessel needs recharging, or your pressure release valve is leaking or your CH system is leaking somewhere.)
  3. Aaaargh - repost in the 'Plumber's Forum' :)

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