1. Visiting from the US? Why not try DIYnot.US instead? Click here to continue to DIYnot.US.
    Dismiss Notice

Additional Cold Water tank to increase hot water flow.

Discussion in 'Plumbing and Central Heating' started by lidster, 30 Apr 2019.

  1. lidster

    lidster

    Joined:
    22 Jun 2012
    Messages:
    64
    Thanks Received:
    0
    Location:
    Leeds
    Country:
    United Kingdom
    Hi All,
    Ive got a vented gravity system. 50 gal cold tank in the loft. bought a new mixer tap for the bathroom sink which is on mains cold, but the hot water is from my tank.
    https://www.screwfix.com/p/bristan-blitz-basin-mono-mixer-tap-with-clicker-waste/410gf

    Flow through the hot side is terrible. a trickle, despite it being suitable for gravity fed systems in the screwfix description. Ive noted that it needs 0.2 bar pressure. I have exactly 2 metres of head to this tap outlet.... possibly im out by 10cm.... the cold feed into the bottom of the hot water tank is 2.6 metres. It needs a non return valve adding - the cold is pushing the hot back into the tank - its all isolated at the moment - just using the coldfor now.

    I am going to replace the isolation valve just under the sink to a full bore one.
    I have also bought a non return valve for the hot but cant see any full bore ones....

    My question is - will the full bore fittings make much difference? The flexy hoses provided into the tap are reducing the pipe diameter anyway.

    Ive also read that flow is increased if I join another Cold Water Tank in the loft - so that a greater body of water is pushing down the pipe. This seems to be debated a lot with most people saying its only the height that matters....

    Any help /advice please?
     
  2. bernardgreen

    bernardgreen

    Joined:
    3 Nov 2006
    Messages:
    25,849
    Thanks Received:
    2,572
    Location:
    Bedfordshire
    Country:
    United Kingdom
    It is only the height that matters as regards the pressure ( aka head ). From surface of the water in the tank down to the tap.
     
  3. Sponsored Links
  4. Madrab

    Madrab

    Joined:
    4 Oct 2012
    Messages:
    8,246
    Thanks Received:
    2,356
    Location:
    East Renfrewshire
    Country:
    United Kingdom
    Water pressure in a gravity fed system is dictated purely by height above a given outlet, hence the saying - meters or ft of head of water.

    Your issue is that you are using mains cold water and gravity hot water and the higher cold mains pressure is restricting the hot water pressure in the body of the tap. Unless you equalise the hot water pressure with the cold you will continue to have issues with a single flow tap, regardless of what you add to the system.

    You need a dual flow tap or pump the hot.
     
    • Like Like x 1
  5. JohnD

    JohnD

    Joined:
    15 Nov 2005
    Messages:
    74,277
    Thanks Received:
    4,290
    Location:
    Crossgates, Europe
    Country:
    Cook Islands
    or run a new cold water pipe to the bathroom from the loft tank.

    It will be less noisy, and will enable your mixer taps to work, and will remove the risk of cold pushing into the hot cylinder and causing the loft tank to overflow.
     
  6. Sponsored Links
  7. polesapart

    polesapart

    Joined:
    27 May 2011
    Messages:
    1,364
    Thanks Received:
    351
    Country:
    United Kingdom
  8. DIYnot Local

    DIYnot Local

    Joined:
    3 Sep 2019
    Country:
    United Kingdom

    If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

    Select the supplier or trade you require, enter your location to begin your search.


    Are you a trade or supplier? You can create your listing free at DIYnot Local

     
Loading...

Share This Page