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Discuss Cold water tank in a flat with a combination boiler?? in the Plumbing Forum area at

  1. vivvov

    vivvov New Member

    But of a puzzle.
    I was away and my partner called and said 'there's a small leak'.
    She lives in an old 1880s terrace that's been broken up into shop (ground floor) and 3 flats..hers is the top flat. She has a combination old Worcester 24i. But there is a coldwater tank in the loft..big old thing..poly (not metal). That's where the leak is coming from...partner has BG home cover and an engineer came out..'not the combi'..then a plumber..'it's your coldwater's not the overflow leaking though...old coldwater tank, somehow leaking from coldwater tank but hard to tell'
    I arrived back and took a look.

    Here's where it gets a bit odd.
    There's a coldwater tank in her flat but she's got a combi boiler???
    I always thought that when the combi and central heating was fitted that they just couldn't be bothered to remove the just left it.
    So I thought..drain coldwater tank, remove ballcock, replace with stopscock and then connect to the 4 exit pipes that seem to supply the bathroom cold, then chop up and remove coldwater tank and re route the 2 mystery over flow pipes that are directed into the top of the present tank into the overflow pipe that runs through the slates onto the roof.
    I turned off the stopcock in the bathroom..that stopped cold supply going to the sink, bath and toilet cistern...I tied up the ballcock to stop it filling the cold water tank and drained the tank...thought I'd leave it til Monday before I did anything else....then the tied up coldwater ball cock loosened enough to refill the cold tank to just above the 4 exit holes and, coincidentally or not??.. suddenly one of the mystery overflows started to flow with cold water.
    Got to thinking maybe the cold water tank supplies the flat went downstairs and the guy is trying to repressurised his immersion tank!!
    He can fill it from the mains but there's also a mystery (to him) pipe teeing off and going somewhere...the cold water tank in my Gf's loft.
    ...and the overflow passing water is him trying to repressurised his tank...and presumably the other mystery overflow is the shop/ the other flat's immersion heater..
    It's a right dogs dinner
    Is the best/ easiest solution to replace the massive old failing cold water tank with a new one quarter the size?
    ...or something more 21st century?
    • Optimistic Optimistic x 1
  2. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    i would say each of the flats have a tank cold supply need to find what there being used for and do they need gravity

    do you have a building maintenance fee / anything like that
  3. vivvov

    vivvov New Member

    Thanks for the reply Shaun..double checked the tank..the 'tide mark' level of the water in the tank reaches the overflow pipe level but, due to all the houses being a bit wonky from 140 years of subsidence, the tank is on a slant and the tide mark is also level with a top corner of the tank at the other end to the overflow pipe...with a slight scale build up on the ballcock valve plus this hot weather making the tank more pliable..there's the leak..over the toplip.
    I'm going to reposition a new ballcock assembly 8 inches lower down the tank wall and ditto for the overflow pipe...take out a lot of extra water/weight but still have the necessary amount of water to cope with need.
    Also I'm going to stick an isolation valve in line with the ballcock valve so as I can isolate with having to go up and down 3 flights of stairs.
  4. Harvest Fields

    Harvest Fields S. Mod Trusted Plumber GSR Top Contributor!!

    It could be for the shop or another flat. Seen that before.
  5. Maryplumb

    Maryplumb Plumber GSR

    Hi Vivvov
    I would say not a dog's dinner but a mutual storage and feed cistern for the 3 flats and shop probably when building converted all the flats had hot cylinders with a vent pipe (your "mystery overflows") going up and over the cistern (tank) but maybe this PVC cistern was installed later when two of them had changed to combis. 4 exit pipes either means each pipe supplies hot cylinder and cold taps to four premises, or they are hot and cold to two flats.
    Lowering the water level is a good idea but essential to make sure there is enough water left to keep two cylinders full while baths running plus any cold taps they might supply.
    Also make sure the tank is properly supported under the whole base as it has already moved and this might be the first sign of trouble, they can split or collapse if not, as Shaun says if there is a factor it would be best to contact them as the tank is probably a mutual responsibility not just the top flat.
    Check new overflow positioned so that ballvalve can never be submerged which could cause contamination of the main.
    The vent pipes are not overflows they are in constant use allowing for expansion of the hot water, escape of air and maybe occasionally very hot water if a thermostat fails. They must be left open to atmosphere or the cylinders could suffer distortion and leak.
  6. fixitflav

    fixitflav Active Member

    It looks like it's the cold water storage tank for your flat and all the other occupants. If you isolate it, let alone remove it, you'll have trouble with your neighbours! You don't say whether she owns or rents the flat, but I'd have thought she'd have been told "her" attic contains a tank supplying other properties.
    Repositioning the ballcock, involving altering the feed pipework seems a lot of trouble. Can't you just bend the arm, or buy a different ballcock? I've seen them with the float on a rod giving several inches vertical adjustment.
    And as somebody else said, is it yours to work (and spend money) on?
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