Gate valves will not stop water flow

Discussion in 'Plumbers' Talk' started by SteveMJ, Apr 14, 2012.

  1. SteveMJ

    SteveMJ Active Member

    As part of my pipe replacement (see http://community.screwfix.com/message/1210466#1210466) I found that the cold feed for the HWC had two valves in series, neither would stop the water flow.  Thinking I could just fix this by changing the washer (if it was a stop cock) I pulled the top off of one, the other I could not undo  (this I intend to try to get a bigger spanner on tomorrow).

    The one I pulled the top off (ie partially disasembled) is a gate valve.  I can't see how this can be repaired - so I assume a replacement is needed .  Can I repair this easily - to save the awkwardness of accessing the pipes to replace?

    What is the difference in application of a gate valvel compared with a stop cock?  Similar function but with very different construction.

    Thank you all again.

    Steve
     
  2. joinerjohn1

    joinerjohn1 Screwfix Select

    Do you mean that when you turn these valves off, the hot water still flows out of the taps? If so, it's because the hot water comes from the cylinder, which will have to drain down, before the water will stop. Have a look and see if there's a valve on the pipe coming from the top of the HWC. If there is, turning this one off should stop the water to the taps (but the water in the pipes may have to drain down before the flow stops)
     
  3. Crowsfoot

    Crowsfoot Screwfix Select

    A gate valve will rarely shut the water off 100% (plumbers know this and will hardly ever use them) stop taps will stop the water 100% (on most occasions).

    A job that I get called to many times is when a diyer turns off their gate valve only to find it still slightly passing, he will then put his spanner on it to gain more leverage only to suceed in snaping off the stem of the gate valve thus leaving the valve in the off position with 50 gallons of water still in the tank above! - Ooooops time to call in a plumber :'(
     
  4. G Brown

    G Brown New Member

    Gate Valves always fail :) They cannot be repaired in situ, just drain the tanks and fit lever valves.
     
    RolandK likes this.
  5. diymostthings

    diymostthings Well-Known Member

    I've never understood why gate valves are marketed - they are useless. Due to their contruction they rarely shut of the supply completely and if not "exercised" regularly (who does?) will invariably "sieze" with the inevitable sheared spindle. A waste of space! As GB says fit quarter turn lever valves. If in a shower feed make sure you get the "full bore" ones (e.g. Pegler). The cheaper ones have a tiny bore which can significantly restrict the flow.

    diymostthings
     
  6. I'm with you guys absolutely. Who fits these things and why? They're not that much cheaper than proper valves, they're invariable seized up, they don't shut off completely and they're chuffin' useless in an emergency. As they're still manufactured presumably the old codgers keep buying them. 
     
  7. SteveMJ

    SteveMJ Active Member

    Level ball valve fitted - in place of former gate valve.  Cost a fiver and took 20 mins or less.

    Many thanks
     
  8. gib.son

    gib.son New Member

    the reason we owd codgers fit um, is because they give a full flow, so for hot water a stop tap wont do and ball type valves leak throu the screwdriver slot after a while, Ok they sieze once in a while and they don't allways shut off,  but when they work they're fantastic, oh yea you've not always room for a lever valve, but if you have I like them too,
     
    swyftie likes this.
  9. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    If we turn the inlet to our immersion off, the hot water stops flowing almost immediately!!

    Mr. HandyAndy - Really
     
  10. swyftie

    swyftie New Member

    Don't know if it's okay to add this here or if I should start a new thread?!!!
    I'm currently changing taps in a school and, as they're so old, am encountering a lot of broken gate valves which I am replacing as I go along (they have boxes of spares so depleting the stock before looking at alternative isolators).
    I'm now facing one that will not close and cannot find any other isolation points along the run of pipe. Isolating the building and draining off isn't really an option as it is being used all summer and would probably take all day to do too.
    Is there any way I can get this valve working again or an alternative way to isolate the pipe?
    I know you can freeze pipes but it's something I've never done and am unsure of - it's a 22mm hot water pipe but because of a faulty TMV no hot water is passing further along so pipes are cold.

    Any advice would be greatly appreciated.
     
  11. KIAB

    KIAB Super Member

    Better to start a new thread.:)
     
    swyftie likes this.
  12. furious_customer

    furious_customer Screwfix Select

    A plumber recently explained to me that over time sediment becomes trapped in the recess of the 'gate' in a gate and prevents is from fully closing.
    Aparrently doing a few sharp turns on and off turns can sometimes clear it out - doesn't alway work, but always worth a try.
     
  13. KIAB

    KIAB Super Member

    Yep,& it's even worse when you drain down a F&E tanks & all crud gets caught by a gate valve, & only solution is cutting out blocked section of pipe to clear blockage.:mad:
     

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