Air in my central heating

Discussion in 'DIY' started by ex_mudmechanic, Feb 3, 2012.

Welcome to the Army Rumour Service, ARRSE

The UK's largest and busiest UNofficial military website.

The heart of the site is the forum area, including:

  1. I had a new boiler put in last winter and it has always made a bit of noise as air goes round the system. Nothing that'd drive you mad, just a bit annoying. I assumed it was normal for a new boiler, but I've been bleeding air out of the rads for over a year now and that really can't be right.

    Do I need to get somoene in, or is there something simple that a complete mong like me can do to rectify it?

  2. When you have been bleeding the air out - have you been putting water back into the system?
  3. Is it a combi... sealed system, or does it have a small tank in the loft or airing cupboard which tops the system up via a ball- valve?
  4. On most boilers there will be bleed points, placed normally high up near the heat exchanger matrixes, one for hot water and one for the heating. Download the handbook for your boiler and all will be revealed.

    However if you heating system is an old fashioned open system, one with a header tank somewhere in the roof, you may have an imbalance problem where the heater pump is too ferocious and draws air down into the system from the header tank. That takes a bit of plumbing nouse to sort out!
  5. The best time to bleed your radiators is when they've been off for a week or two at the height of summer and the air can rise to the top. Bleed until the sputtering stops and then close the valve. If you tap along the radiator front and back to dislodge any bubbles caught on the inner surface and bleed again, you'll be surprised at how much additional air comes out. We have panelled but ribbed radiators at home and I just roll one of those plastic wallpaper edge flatteners across them a couple of times. But anything that sets up a good vibration will do. Then don't forget to top up. Very important.

  6. It's more common that water will be pumping over when the system is running i.e. if you look at the vent pipe(the one which goes up and over the tank) hot water will be coming out of it and back into the tank.

    If not, try inflating a plastic bag and hold it tightly over the vent pipe, if it deflates, then what Cerrunnos said.
  7. I always thought bleeding the radiator furthest from the boiler was the way to do it. But I ain't a plumber!
  8. No, I thought it happened automatically via the header tank.

    It's not a combi, there's a header thank in the loft. I didn't want a combi, having had one years ago and it was a nightmare, however I hear they're pretty good nowadays.

    I think you may have hit the nail on the head there. I remember the guy pointing it out to me when he fitted it, but it went in one ear and out the other!

    Good advice about leaving the system off for a week, but that won't be happening any time soon! And when it comes to summer, I tend to forget about the heating until it starts gurgling again in October!

    I'll definitely try giving the rads a tap with something though, sounds sensible.

    I'll give that a try too. Sounds like a trip up to the loft.

    Thanks for the replies lads. I'll let you know how I get on.

    Any further advice/comments welcome.
  9. Imagine a horizontal circle of pipe full of water with a pump on it.

    The pump is pushing the water around..... till the half way mark.

    Then the other side is sucking the water back towards the pump.

    The point where blow becomes suck is called the neutral point and in theory this is where the vent should be.

    In reality there are a lot of daft buggers who couldn't care less and you get one or the other situations described, pumping over or air being sucked in.

    Both these faults are serious and will result in the radiators suffering from corrosion very quickly, plus premature failure of pump and motorised valve etc.

    Whoever did this should be compelled to come back and sort it, plus a good chemical clean then dosing the system with inhibitor.
    • Like Like x 1
  10. rads can make alot of noise if they have build up of magnenite(?). that black sludgy water, when you drain rads. as mentioned above get whole system drained and an inhibitor put in the system.
  11. Porridge_gun

    Porridge_gun LE Good Egg (charities)

    Drill a series of small holes in the top of each radiator to allow the air to escape. As its in a radiator the air will be warm so will rise and make its way out of the radiator.

    Seal up the holes afterwards with either plastacine, bogeys or blobs of weld.
    • Like Like x 2
  12. You might have a gas in the pipes problem. To put it simply if you have corrosion in the system it will produce Hydrogen gas, other things can happen as well you could actually have bacteria in the system producing methane gas. Both quite common problems.
    Buy some Fernox or equivalent Preventing Coldspots I don't work for them by the way. It was my specialisation once up on a time though.
    Stick some in the hedder (careful it is for the heating and not the domestic water). drain off some of the system and or (depending how much gas/air is in the system) just vent the rads, get it into circulation anyway. Re-vent a few days later.
    You could see if it is hydrogen or methane being produced but I would not recomend it. Once saw someone light the vent from a rad in a house on park lane london. The flame setfire to some early 19th century wall paper and damaged a picture. Result £12,000 damage and that was in the 80's!
  13. If the set point of the central heating is too high, it may be kettling (the water is actually boiling in the boiler) it should be set to around 60 degrees C. If it is kettling you get a rumbling sound coming from the boiler, usually a sign that the pump has failed. It should be pumping the cooled return water back into the boiler.
  14. Was going to say the same thing - check the small tank in the loft - sometimes the ball cock sticks and not enought water gets through the system
  15. Cant you just bleed the radiators? Small screw at the top right of the panel with a plastic directional hole. Unscrew with a container placed under to catch the water.