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Discuss Sealed system Air and leaks. HELP! At wits end. in the Plumbing Forum area at

  1. Mikmikmikmik

    Mikmikmikmik New Member


    My heating system was changed from a vented to unvented OIL system.

    I have a magnaclean, nearly all the radiators are new.

    The maganclean is cleanish after months of use.

    I keep getting air in my system, and before you chastise me, I swear I cannot see any leak.
    The pressure keeps dropping too, until it gets to about 0.3 bar and then stays there.

    The tallest radiator is four floors up from the heating pump.
    The hot tank is on the third floor where the pipes from the boiler go first and then to the second floor to the manifold.

    The pipes are micro pipes to the radiators from the manifold, but I think 3/4 inch from the boiler to the manifold.

    I am grateful for any advice given including what kind of heating pump I need to pump up 4 floors.

    Thank you.
    Last edited: Apr 30, 2018
  2. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    How long since the work was done ?
  3. S.P.S.

    S.P.S. GSR

    It’s not usual to have to top the pressure up a couple of times on bigger systems, micro bore can be a pain. Trapped pockets of air can take a little while to clear, automatic air vents will clear the air and pressure will drop. Some will dissipate also. Eitherway call back the crew that fitted it all?
  4. sammathias

    sammathias Plumber GSR

    all old central heating pipework converted from open vented to sealed...I will probably get a lot of hate for this but personally its asking for trouble. you probably have small leaks under floorboards causing pressure drop and air getting sucked into system.
  5. Mikmikmikmik

    Mikmikmikmik New Member

    I appreciate your replies. The air doesn't happen until about 45mins into the cycle, but then there is a large thumping gurgling sound. I have air vents in, one on outlet from boiler and one above hot tank.
    The air only happens when the heating is on but who knows, maybe it is only pumped round to where I can really hear it by the pump when the heating is on
  6. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    That's not air sounds like it's ovetheating
  7. Stigster

    Stigster Plumber

    It would be worth checking that the seals at the circulating pump are in good condition and tightened properly. I have seen air ingress caused on the vacuum side of the pump pulling in a steady stream of air into the system without leaking any water. We also had one of our plumbers on the forum getting air ingress and being unable to locate it. I suggested to check the pump seals and it did turn out to be that. However this is usually a slow process that takes a while to show a drop in pressure but still worth checking.

    Also ShaunCorbs could well be correct and it's an overheating problem so that needs investigating. Have you checked to see if the pressure relief valve is discharging water? If there is an expansion issue, as the water temperature increases so does the pressure. If the expansion vessel is undercharged (or possibly a faulty PRV) the expansion has nowhere to go and cause PRV discharge.
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