Air in Hot water cylinder

Discussion in 'Plumbing and Central Heating' started by Superwidget, 27 Sep 2003.

This topic originated from the How to page called Problems associated with noises from the central heating system.

  1. Superwidget

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    I have completely drained my CH system to add in a new radiator, then refilled and bled all the radiators. Unfortunately, I do not have any hot water and the hot water cylinder seems to be empty / full of air. The automatic air bleed appears to be working correctly. Can anyone advise what I can do? Thanks. :(
     
  2. oilman

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    What type of system do you have?
    If it is a normal vented hot water tank - ie with a header tank in the loft, it is fed from this tank, and the header tank is fed from a connection to the main, you would have no need to drain it to add radiators. Is it a thermal store? Is it an unvented tank?
    For an unvented tank (also no need to drain, turn on the cold water feed and turn on a hot tap. Air will come out until it is full. For a thermal store, is it a sealed system, or does it have its own header tank. Again you ould only have to drain this if it was a direct heating type, otherwise no need to drain.
     
  3. masona

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    Is the radiator working and are you getting water out of hot taps?

    As oilman said "what type of system do you have?"
     
  4. Superwidget

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    I have a normal vented hot water tank - ie with a header tank in the loft, it is fed from this tank, and the header tank is fed from a connection to the main.
    It's gravity-fed and does not have a motorised valve. We have bled the radiators 3 or 4 times - each time we find more air in them and the automated venting valve activates every so ooftenb when the water pump is on (i.e. partially emptying system only).
    We have hot radiators but no hot water from any taps + the hot water cylinder is cold. Thanks for your responses so far - any suggestions now???
     
  5. breezer

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    this will need confirmation, but i think this is one of the occasions when you put a hose on the cold tap and put the other end on the hot tap and turn them both on, but you have to have some one in the loft to make sure the expansion tank doesnt over fill. the idea is it forces all the air out of the cylinder
     
  6. masona

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    Sound like you have a airlock.

    When the water tank empty,air got in creating a airlock.You need to get a water main pressure back up to the hot tap with a hose somehow and force the air out into the tank.If it a bath/shower mixer,I have made a connection on the shower pipe outlet with a garden hose & turn the shower lever to shower position and open up the hot tap with the cold tap shut and turn on the water main on.This way you don't get wet instead of the old method with towel. Don't do it for too long as the water level will overfill out the overflow
     
  7. breezer

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  8. masona

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    ahhh, 1 minute late was I :!: :)


    Also I forgot to mention, make sure the cold storage tank is getting water + the ballcock is okay.
     
  9. oilman

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    Superwidget, are you getting cold water from your hot taps? If not follow breezer and masona. f you are getting cold water, then any airlock is in the heating side not the "water to tap" side. You are getting hot water to the radiators, what controls the flow to the hot water tank? Do you have 2 pumps? If not then you must have a valve or were you saying earlier that you have gravity heating to the hot water cylinder?
     
  10. Superwidget

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    Many thanks for all your useful suggestions. After bleeding all the radiators & activating the automatic bleed valve many times the hot water in the taps has started to work - although there still appears to be some air in the system from the noise of the pump. We have tried starting, stopping and changing the speed of the hot water pump several times which appears to have speeded up the rate of air removal by the automatic bleedvalve. Having examined the system more carefully there appear to be TWO water pumps (one in boiler & one next to hot water cylinder) and NO motorised switch over valve. One pump comes on when room heating is selected and the other pump comes on when hot water heating is selected. Is the system a little unusual as most systems in DIY plumping guides have either a switch over valve or gravity feed. Should I add a switch over valve or stay with two pumps ? Is there anything else I can do to remove trapped air or should I leave the automated bleed valve to do its job ??
     
  11. breezer

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    have you tried bleeding the pump?

    (just like you would a radiator, except you turn the big screw in the centre of the pump)
     
  12. masona

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    Bleeding the radiator will not make any difference to the hot water tap.I still say try and force the rest of the air out as in my previous post.
     
  13. homeDIYonly

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    Hopeing for some help!

    Firstly the system I have in my house - I have a main water talk in the loft, which feeds the hot water cylinder on the first floor. I have a water pump that feeds the hot water for the whole house connected off the hot water cylinder - so when any hot water tap opens the pump kicks into action.

    So my issue I had a leaky hot water tap and turned the mains cold water supply off from outside my house and then emptied the water of the cylinder and main water tank in the loft. so no water was coming through my taps. I replaced the washer and then turned the water back on from the mains.

    Now my hot water is not coming at all! from what I have read already there is clearly air in the system but when I try the U technique with the cold water is just stops the pump working.

    Any suggestions - I am not even sure the water cylinder is full - it definately has water because I hear it filling but doubt very much its full - I think it full of air! is there a way I can air it? so the pump is not effected!

    completely lost and this is now day 2 without hot water....
     
  14. picasso

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    stick to one post mate , its confusing for everyone when you post the same problem in different places.
     
  15. Nige F

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    And Year 9 since the original post :mrgreen:
     

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