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Discuss Central heating system loosing pressure in the Central Heating Forum area at

  1. chris301up

    chris301up New Member

    Can anyone please advise

    I have a central heating system comprising of 7 radiators and a Saunier Duval Thema F23 combination boiler

    During the spring and summer period the pressure remains constant at around 1 - 1.5 bar and I don't usually have to re-pressurise it

    However, during the autumn and winter period, the pressure drops fairly rapidly and I usually have to re-pressurise every 1 - 2 days or so.

    I rarely use the central heating , unless it's absolutely necessary, as I simply cannot afford it, so tend rely solely on the gas fire. This doesn't prevent the pressure dropping though even when it's not in use during the periods in question.

    I have checked for any leaks as best as I can but am at a bit of a loss why this only occurs

    Any advice would be greatly appreciated
  2. Harvest Fields

    Harvest Fields Trusted Plumber GSR Top Contributor!!

    Have you checked the pipe that pokes out the wall outside? Is this dripping when the heating is on. Also does the pressure rise when the heating is on?
  3. chris301up

    chris301up New Member

    I know the pressure relief outlet doesn't leak but I haven't checked the pressure rises when heating is on. Will do that and post result. Thanks
  4. chris301up

    chris301up New Member

    Right. I've just run the CH for about half an hour or so and can tell you that the pipe protruding through the wall is not dripping, but trickling out in a steady stream. The pressure has also risen to just about 2 bar. I suspect a serious problem??
  5. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Not a serious problem but it needs addressing rather than waiting
    • Agree Agree x 1
  6. Harvest Fields

    Harvest Fields Trusted Plumber GSR Top Contributor!!

    As above mate get it checked
  7. chris301up

    chris301up New Member

    Further to my earlier posts I've just noticed that the water trickling out of the pipe protruding through the wall is hot. Didn't notice this before!!

    I have been awaiting the possibility of boiler replacement under the government scheme, but apparently I'm not eligible for it?
    Will have to see about having this boiler sorted in the interim.
  8. Stigster

    Stigster Plumber

    It could be as simple as having the expansion vessel recharged and possibly a new Temperature & Pressure relief valve if it won't seat properly. Not something you can do yourself but not major works either.
  9. chris301up

    chris301up New Member

    I have just had a guy round to have a look at the ongoing issue but he can't seem to locate the expansion vessel recharge valve anywhere.

    The only one he can find is located on top of the pump unit, which is the same as a tyre valve, but there is insufficient room to get a air pump to attach to this as there simply is insufficient room

    Does anyone know where this may be located or is this the only one within the system?

    Attached Files:

  10. chris301up

    chris301up New Member

    Right. Just an update.

    I decided to take the left hand side panel off the boiler and have managed to locate the expansion vessel. For anyone else who owns a Saunier Duval F23E Thema, it's red and situated immediately behind the burner unit behind the boiler itself. The main pipe is clearly visible entering the centre of the expansion vessel from the front and you can 'feel' the valve on the top left hand side. Around 11 o'clock,

    I have drained the central heating system and then topped the air back up to 1 bar but, when turning on the central heating, the water still comes out of the pipe on outside wall.

    I will say it doesn't appear to be running quite so much, but it is still more than a trickle.

    Would anyone say that it may be worth replacing the pressure relief valve?
  11. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Gas safe engy
    • Like Like x 1
  12. chris301up

    chris301up New Member

    What does that mean. "Gas Safe Engineer"?

    My son-in-law's Dad is registered as 'gas safe' and, if I can get hold of him was going to ask him to check it out.
  13. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Best option as you can't really take the cover off unless you are qualified
    • Agree Agree x 1
  14. chris301up

    chris301up New Member

    The cover doesn't have to come off for the PRV. It's underneath
  15. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    No but you've already removed the cover to get to the expansion vessel ;)
    • Like Like x 1
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