Mystery hot tank overflow - any ideas/suggestions?

Discussion in 'Plumbing and Central Heating' started by Stevel, 2 Apr 2012.

  1. Stevel

    Joined:
    10 Aug 2004
    Messages:
    39
    Thanks Received:
    0
    Country:
    United Kingdom
    My Setup:
    Electric boiler, heating HW / CH - I have a gravity-fed hot tank and header tank in loft.

    My Problem:
    When turning on the HW for a downstairs shower, after between 12-24 hours, the header overflow starts trickling with water. The ball valve is operating fine, but the expansion pipe for the cylinder leads to the header tank.

    I have tried really hard, but can't work out why the overflow is, er, overflowing. Pressure? Air intake? Leak anywhere?

    The pressure is on for me to tile the shower, so would really appreciate any help in solving this one!
     
  2. picasso

    Joined:
    8 Apr 2008
    Messages:
    6,252
    Thanks Received:
    1,361
    Location:
    Essex
    Country:
    United Kingdom
    cold mains water and gravity hot water feeding the shower ?
     
  3. TonyW2

    Joined:
    24 Dec 2008
    Messages:
    647
    Thanks Received:
    67
    Country:
    United Kingdom
    But if that pressure difference into the shower mixer was the source of the extra supply into the feed tank, the shower would always deliver only cold.

    OP says it happens after 12-24 hours. Are you sure that the ball valve is shutting off? It may be that at most times, water use is sufficient to use the excess supply and that it builds up when there has been no use for a long period.
     
  4. leakydave

    Joined:
    2 Nov 2005
    Messages:
    788
    Thanks Received:
    72
    Location:
    Gloucestershire
    Country:
    United Kingdom
    Cylinder coil leaking water from one cistern to another?
     
  5. Space cat

    Joined:
    9 Sep 2007
    Messages:
    3,862
    Thanks Received:
    74
    Location:
    Newcastle upon Tyne
    Country:
    United Kingdom
    That would be my first guess. Test it. Next time the header tank is overflowing, don't use the shower. Don't use any hot water at all; just scoop a jugful out then wait to see if it fills up again. :idea: :idea: :idea: The best time to do this would be last thing at night.
     
  6. picasso

    Joined:
    8 Apr 2008
    Messages:
    6,252
    Thanks Received:
    1,361
    Location:
    Essex
    Country:
    United Kingdom
    If you throttle the cold down enough you can roughly balance the hot and cold, its bad idea to install like this but its seems to be a favourite short cut for diyers,

    the reason I asked about the hot/cold supplies is the check valve in the shower could be passing letting cold flow back up the hot supply to the tank, or any where the mains water and hot meet ie kitchen mixer, washing machine installed with y connector ect.
     
    • Thanks Thanks x 1
  7. Stevel

    Joined:
    10 Aug 2004
    Messages:
    39
    Thanks Received:
    0
    Country:
    United Kingdom
    I had two lever-style isolation valves for the hot and cold put into the ceiling of the DS shower room. The overflowing only occurs when the hot valve is open, and can be stopped when it is closed (not instantly, but after a few minutes).

    The 12-24 hours reference is to when this valve is opened. We have had hot water going to DS and the US Bathroom for over a year with no problems.

    I should also add that the valves are the end-of run.

    This probably makes this even more odd!

    Thanks for the ideas already - I will turn hot valve on and 'jug out' the header tank to see if it is the ball valve. Is is worth somehow collecting water from the expansion pipe?
     
  8. foxhole

    Joined:
    14 Mar 2006
    Messages:
    8,457
    Thanks Received:
    900
    Location:
    Kent
    Country:
    United Kingdom
    Is the overflow pipe above header tank securely fixed, mine came loose and dropped causing siphoning and overflow of tank whenever it was heating.
     
  9. Stevel

    Joined:
    10 Aug 2004
    Messages:
    39
    Thanks Received:
    0
    Country:
    United Kingdom

    This actually makes a lot of sense. The shower certainly is a 'mixer' type, with two handles, one for flow, and the other for temperature. Is it worth adjusting the temperature on the shower so it is v cold, as in, shutting off the hot?[/quote]
     
  10. Space cat

    Joined:
    9 Sep 2007
    Messages:
    3,862
    Thanks Received:
    74
    Location:
    Newcastle upon Tyne
    Country:
    United Kingdom
    Well that changes things a bit. You can forget about the ball valve for now. Water is backing up the hot pipe from the shower - very slowly since it takes at least 12 hours for it to reach the overflow. The fact that you can stop the dribbling by shutting the hot valve pretty much clinches the diagnosis. The question now is this: Where is the excess water coming from? :confused: :confused: :confused:
     
    • Thanks Thanks x 1
  11. Stevel

    Joined:
    10 Aug 2004
    Messages:
    39
    Thanks Received:
    0
    Country:
    United Kingdom
    HUGE THANKS to PICASSO - your hunch was absolutely right. This is what we did to test and solve the problem:

    Put the HW to advance, filling up the cylinder with hot.
    Opened the hot iso valve.
    Turned shower on, and turned it to hottest setting.
    Checked hand temperature of hot by valve - hot to touch.
    Cup of tea.
    Sudden influx of water on kitchen roof from overflow pipe!
    touch hot valve - now very cold!
    Turned off Hot at valve
    flushed toilets to give Header Tank some space.

    Will now search out new shower mixer and 'file' old one. Never liked it anyway!

    Thanks again to all those who contributed a solution!
     
  12. TonyW2

    Joined:
    24 Dec 2008
    Messages:
    647
    Thanks Received:
    67
    Country:
    United Kingdom
    12 to 24 hours to drink tea???? ;) :) :)
     
  13. Stevel

    Joined:
    10 Aug 2004
    Messages:
    39
    Thanks Received:
    0
    Country:
    United Kingdom
    I've done a bit of research, and it would seem I could add a check valve to the hot pipe. Is this hiding the problem, or would this be a good move?
     
  14. duffin

    Joined:
    19 Oct 2008
    Messages:
    136
    Thanks Received:
    24
    Location:
    Warwickshire
    Country:
    United Kingdom
    don't bother with a check valve- although this would work. change the mixer and make sure it's suitable for gravity systems.
     
  15. linkyplumb

    Joined:
    8 Sep 2008
    Messages:
    1,349
    Thanks Received:
    168
    Location:
    Hampshire
    Country:
    United Kingdom
    High pressure area?

    Had this once with a combination cylinder. At off peak demand pressure got to over 12 bar and caused ball valve leak, thus overflowing.
     

Share This Page