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Vented central heating system queries

Discussion in 'Plumbing and Central Heating' started by Giles Mann, 25 May 2020.

  1. Giles Mann

    Giles Mann

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    I live in an old house that was converted into flats. Our flat has a combi boiler as do 4 of the other 8 flats. What I didn't realise was 3 of the flats are still on the old communal heating/hot water system - I think that this is a vented system.

    In the attic there are two plastic (old looking) tanks - they are the same size. One with warm water in, the other with cold water.

    After doing some research, I think that the tanks are as follows:

    Warm water tank - central heating header tank:
    - Has two copper pipes connected near the bottom (I suppose the connections to the central heating system)
    - Has a ball cock valve for mains water supply
    - Has a upside down U-shaped copper pipe into the top - I believe this is the vent pipe. The end was submerged below the water level when I looked at it (I think this is an issue based on what I've read)
    - Has an overflow pipe which has sometimes had water running out over the last year (again, believe this to be an issue)
    - Even the fact that the water is warm - I think is a problem.
    - Shouldn't this tank be much smaller than the cold water storage?

    Cold water tank - cold water storage:
    - Ball cock mains feed
    - Cold water outlet to bathroom taps
    - Outlet to feed 2x hot water cylinders on ground floor (presumably this feeds hot taps by gravity pressure)

    Apparently the remaining 3 flats are considering going self contained so the communal system will become redundant - the bills are very high for them from what I've heard.

    My main concern is having what I think to be a dodgy and old system with tanks of water in the attic. I have read horror stories of water boiling and rupturing tanks. I really think that we should get someone in to check it is safe.

    Sorry for long post - was hoping you guys might have an opinion on this.
     
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  3. denso13

    denso13

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    Should be a gap to the water. Lower the water level or shorten the pipe.

    Could simply be a ballcock issue.

    As long as it isn't too hot. The water from the heating system can expand in to the cistern so could be warm.

    Usually, but it doesn't really matter.

    Doesn't sound dodgy to me at all. May need some things checked but seems like a normal system.

    By the way, they are cisterns, not tanks :sneaky:
     
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  4. denso13

    denso13

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    Actually, if this feeds two systems it may be why the feed and expansion cistern is larger than normal.
     
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  5. Giles Mann

    Giles Mann

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    Thanks denso. That has put my mind at rest a bit.

    I think I will reduce the pipe length a bit (to above overflow level) so it cannot go below water surface, even if ball cock valve doesn't operate properly. What are the implications of this as it is - oxygenating the water in the cistern ;) and causing corrosion in the system?

    I will get it checked out - another thing I noticed sometimes is a screeching/gushing sort of noise coming from the attic when the communal heating is on which can't be good.
     
  6. Giles Mann

    Giles Mann

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    Are you referring to the two hot water cylinders? I thought that these were fed by the other cistern.
     
  7. denso13

    denso13

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    Sorry, no, this bit.

    They would normally have one connection. It has two so I was thinking if it fed two systems (as the other cistern does) it may be why the (heating) cistern is larger than usual.
     
  8. Hugh Jaleak

    Hugh Jaleak

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    If the communal system becomes redundant it would be prudent/expected that the installer carrying out the alterations would empty/disconnect/abandon these cisterns.

    There have been incidents with boiling water yes, but as far as I am aware on these occasions it has been linked to a faulty immersion heater boiling the contents of the hot water cylinder, which in turn has heated the contents of the cold water cistern supplying the cylinder. The plastic cistern has then softened, and collapsed, emptying its deadly contents through the ceiling into the room below.

    Without knowing the arrangements in the other flats it is difficult to say whether there could be a possible issue. Modern immersions heaters should have a safety cutout built into the heater to switch it off if a fault occurs.
     
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