Always have air in rads

Discussion in 'Plumbers' Talk' started by SLIPSHOD SLAPDASH LTD, Jan 1, 2008.

  1. My mums 1 bed flat has 4 rads and a towel rail on a conventional system (Potterton Neataheat boiler). The building is about 20 years old. Apart from the lounge rad thats on the end of a run all rads fill up 100% with air. I can bleed them and within 15 min there cold. When we re-fitted the bathroom and replaced the rad with a towel rail i fitted a auto blead. This packed up after a month (probably over use!) 2 plumbers have checked but could not find anything. The expansion tank is only 1 ft above the boiler. Could air be being sucked in the expansion pipe ?. Could this pipe be extended so its in the water ? The tank is filling. TRV's are fitted to all rads except the bathroom. This may have been like this since before she moved in
  2. mrj

    mrj New Member

    If this problem has only appeared since you fitted the auto air bleed I would suggest that you screw the cap down tight on it to see if this stops it. If this works its because the auto air vent is letting air in instead of out. This happens when it is on the suction side of the pump.

  3. Captain Leaky

    Captain Leaky New Member

    If the system is old and full of sludge it could be gas.

    Don't go altering the expansion pipe.

    Make sure the pump is on it's slowest speed.

    Is the header tank constantly filling ? If so you may well have a leak if the water is being lost that quickly - could be under the floor somewhere.
  4. R849

    R849 New Member

    > If the system is old and full of sludge it could be

  5. Hi, the problem was there before the auto bleed valve was fitted. There is no leak. Its a first floor flat. Most pipes are surface and the expansion tank does not appear to be constantly filling. I have tried different speeds on the pump. Most times the system is noisy because of the air. The system was flushed through when the bathroom was done ( not a powerwash, just a hose out the window)
  6. Captain Leaky

    Captain Leaky New Member

    Just hosing thru wont do much. Take each radiator off and thoroughly hose them out. Hydrogen gas is created when there is a lot of sludge.
  7. Would that smell though ?
  8. heatyman

    heatyman Well-Known Member

    Do youhave pump turned to lowest speed? If it is not, it could be pumping over with such a low static head.
    Converting to a sealed system would probably cure the problem.
  9. HOTDOG ø

    HOTDOG ø Active Member

    Tell me heatyman, can any system be converted to a sealed system? I have a Potterton Neataheat with gravity h/w and pumped c/h. Can I have an expansion vessel installed instead of the header tank? Obviously I would get my local plumber to do it.
  10. heatyman

    heatyman Well-Known Member

    You would need it to be fully pumped, and make sure the boiler is rated for the pressure you intend to run at.
  11. duggie121

    duggie121 New Member

    If you turn the central heating completely off (no pump running, then get someone to hold a bottle of water on the expansion pipe (end of pipe submerged in the water) now turn the heating back on if water is sucked up the expansion pipe this is your problem. If this is the case you need to raise the tank and expansion pipe, if you have no room to do this you need to convert to a combined air and feed system.
  12. Thanks Duggie, i will try that next time i visit.
  13. doitall

    doitall New Member

    If you replace the water with air where does the water go

    Tell us about the cylinder and storage tank.

    Have you check the SV or overflow is not passing water.

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