Pump Gate Valve - how tight?

Discussion in 'Plumbing and Central Heating' started by InMyHO, 28 Sep 2016.

  1. InMyHO

    InMyHO

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    I shut off the pump gate valves so that I could service my central heating pump last night. These stop the water as removing the motor assembly splits the wet part of the pump in half? Did the valves work? Did they heck! So questions for anyone who does this more than the once that I have then...
    • Why are these valves so bad at shutting off the water?
    • Just how hard are you supposed to have to tighten them to completely cut the flow?
    • What tool do people normally use to shut them (to get anywhere near enough torque to shut I used a long adjustable spanner) and why do they have a tiny little square heads to tighten rather than something more useful?
     
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  3. oldbuffer

    oldbuffer

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    1. They depend on a wedge shaped piece of brass moving up and down in similarly tapered barrel. It doesn't take much sludge / grit to stop them screwing fully closed. They are better if mounted so that the inlet and outlet are in vertical alignment so that muck tends to wash through.

    2. In theory the red "disc" handle should provide sufficient leverage. In practice, a pair of grips on the red disc, or remove the disc and a spanner on the flats of the spindle generally moves them. The spindles are prone to shearing where they join the wedge, so too much force causes damage. Its largely a question of feel. A six inch long spanner with medium force is about as far as I'd go. Try the old trick of tightening a fraction first then opening, sometimes "cracks" whatever is holding it. If the valve is a write off, you still need to be careful not to damage whatever its attached to. For changing a pump I'm usually happy enough it slows the flow to a trickle, sufficiently weak to be caught by a wad of old towels. Prepare new pump, with body in correct orientation, turn valves off as far as possible, towels all round, slacken pump nuts. If no deluge, whip the old pump off and the new one on. If deluge, bung, drain down or freeze and change pump valves while at it.
    3. Usually end up using a small spanned on the spindle flats.

    4. They have small square heads because if they were any bigger no one could assemble the valve.

    After changing pump, check and repack glands if necessary, open valve fully then close back about 1/4 turn.
     
  4. InMyHO

    InMyHO

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    Thanks OB really useful. I don't have any red disc handles. They were never fitted. It makes sense that this is what they were designed for though. Good to know some idea about torque limit. Thanks again for a thorough explanation.
     
  5. ollski

    ollski

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    I dont think I've ever had pump valves over 2 years old hold the water. Very rarely even try to be honest as they will probably need cutting off anyway, might as well bung and change the lot when required.
     
  6. Agile

    Agile

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    Like any other valve, pump valves need to be exercised ever three months.

    That stops the mating surfaces from getting dirty and ensures when you need to use them they work properly.

    Tony
     
    Last edited: 29 Sep 2016
  7. Stadan20

    Stadan20

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    So would you exercise every trv , lockshield , gate valve , Iso valve , tap , shower , internal stop tap , external stop tap , blending valve , non return valve etc every 3 months ? ? ?
     
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  9. InMyHO

    InMyHO

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    If people don't mind me having a rant... Why doesn't anyone design plumbing fittings that actually do their job? I mean the point of these valves is to sit there for years doing nothing and then to work. I appreciate that probably no-one reading this is a plumbing fitting designer but really the utter absence of progress is maddening. Please don't tell me that we can't because I have spent a life sending designers back to their (virtual) drawing boards reminding them that they could. It only ever took work; nothing that looked impossible ever was. Plumbers have to operate with what they are given and what the regulations say - it's not their fault. The industry though has to take responsibility. Can anyone think of another business where you would have an equivalent situation - "yes we always fit valves but no they never work when you actually need them"? Would we accept that response for airbags in cars? As I said, don't mind me I'm just having a rant.
     
  10. ollski

    ollski

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    The main reason is that nobody would pay extra for them. There are commercial valves that need to work and do but in a domestic situation there is no need to spend the extra. Also they are tested on clean 'ideal' condition situations which rarely exist in the real world.
     
  11. Agile

    Agile

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    Yes, in an ideal world.

    But the main problem ones are gate valves and stopcocks. The latter, not working, can create an uncontrolled flood!

    Better valves like the Pegler for example do usually work after a time but they cost over ten times more than the cheap Italian ones.
     
    Last edited: 29 Sep 2016
  12. polesapart

    polesapart

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    If I install this [​IMG]it may work in 10 years time


    This upload_2016-9-29_12-12-23.jpeg probably will work in twenty years time



    and this upload_2016-9-29_12-17-56.jpeg is good for 50+ years.





    How many of these will be working after ten years?

    upload_2016-9-29_12-23-15.jpeg
     
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  13. polesapart

    polesapart

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    And "Oldbuffers" post above deserves 5+ stars.
     
  14. InMyHO

    InMyHO

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    I would be careful of such benchmarks polesapart. The phone is designed to be used continuously. It will withstand many millions of discrete operations before failing. They are kept in pockets and subject to regular shocks when banged around and dropped. They undergo rapid repeated temperature changes as well as being put under pressure when sat upon or squashed. If you take into account that the phone has an array of functions and that it is portable then its longevity is simply staggering. Most will fail because they are dropped or damaged rather than through fatigue and those that do wear out are more often let down by batteries than any other component and as battery technology is improving continuously these issues will disappear. The heating valves are bolted down indoors, have one function and essentially are tasked to simply survive for ten years and then work - which they fail to do it seems. If I were a central heating valve designer I wouldn't be looking toward an iPhone and gloating to be honest.
     
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