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pressure limit valve- WHERE?

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  • pressure limit valve- WHERE?

    For at least 4000 doubles now, the mains water pressure of my house has been at a steady 4 bar at idle, registered on the gauge of my Futurmat. I have not fitted a pressure limiting valve because of this constant.

    Several days ago the pressure started to register a fair bit higher. Currently it is 5 bar but yesterday it went as high as 6 bar and maintained this reading for much of the day. It hasnt gone back to its "usual" 4 bar. I bought a 350 kPa pressure limiting valve from Bunnings yesterday and tomorrow will get some fittings to allow it to be plumbed-into the 1/4" water line.

    I would like to know two things:-
    1) What could cause this to occur after several years of lower readings? I am assuming that the gauge is (and has been)  working correctly in all this and that there is indeed water of a higher pressure now being supplied to my house.

    2) Where in the water line is the optimum location to fit the 350 kPa pressure limiting valve?

    I have a twin undercounter water filter system which feeds filtered water to a commercial ion-exchange softener unit. The instructions on the limiting valve suggest to fit a strainer in the system before the valve. My thoughts are that the filters would do this if the valve was fitted between the filters and the softener but then the filters (which should and ***do have a form of limiting valve fitted before the water gets to them...to protect the system from too much pressure)....perhaps would not be protected from water of too high a pressure.

    Reason tells me that if a limiting valve is placed in the system towards the end of the system that it would limit the pressure THROUGHOUT the system....but I am not certain of this. Can anyone with knowledge of this sort of physics clear this up for me?

    ***It could be that the current valve that is fitted as part of the twin water filter system has been keeping the pressure to the machine at 4 bar and is now ailing....am I grasping at straws??

    Thanks,
    Paolo

  • #2
    Re: pressure limit valve- WHERE?

    Hi Paolo,

    when we used to fit these in HIgh rise apartments they were fitted to the water inlet for each unit but in your case fitting it after the softner makes as much sense as anywhere. If you do this then your filters still get the benifit of full mains pressure to allow for losses and your pump gets a nice stable inlet pressure. Dont forget you may need to increase the pressure on your pump relief valve (if fitted) to allow for the reduced inlet pressure.

    Pressure fluctuations on mains can be caused by several things more normal is a drop in pressure (caused by excessive usage other than at your place) than an increase. An increse may have been caused by a temporary change in water source by your water board or a pump or valve control malfunction or even a permanent change to the setup. Water boards use pressure limiters as well. A pressure limiting valve will solve this but like all valve long term need a little looking after in the long term (5-10 years) as if it sticks shut you will starve your pump of water

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    • #3
      Re: pressure limit valve- WHERE?

      Thanks Beanflying,




      Originally posted by beanflying link=1226182936/0#1 date=1226192392

      If you do this then your filters still get the benifit of full mains pressure to allow for losses
      The filter suppliers include a nylon(?) PLV in their twin under-counter setups and state that in the event of flooding, insurance companies will not payup if there was no PLV fitted before the filters.

      I suppose I am wondering that if a PLV is fitted before the water gets to the filters, does this control the pressure to the softener and the espresso machine as well?

      Are the nylon ones as good as the brass PLVs? Can either be serviced?

      Cheers,
      Paolo

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      • #4
        Re: pressure limit valve- WHERE?

        The only problem with fitting the PLV before the filters are that as they start to clog the pressure loss across them increases so the pump inlet pressure will reduce.

        With some of the brass ones we were using the top could be dropped to get to the spring and valve seat for a scrub and polish if required or a spring replacement but most plumbers would treat them as a throwaway item.

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