I am installing a water pressure reducing valve right after water meter:

  1. Should I install a back flow prevention unit as well, & where?

  2. Should I also install a bypass line in parallel to switch to, in case the reducer fails, or will the failing reducer still allow water to flow through with satisfactory pressure no matter what?


Water pressure reducing valves are simply pressure regulators, in the cases I have seen when these fail it has always been to full pressure , but there is another failure that is not the regulators fault. Debris in the water line can collect and create a blockage that can severely limit the flow or even stop it. I would not spend $ on a back flow valve that has to be inspected but a check valve after the regulator can be a good idea.

To prevent debris building up a string filter prior to the PRV or regulator will prevent the chunks from I’m getting into not only the regulator but your valves inside your home.

  • Installed the water pressure reducing valve but seems like it’s not working properly, as in REDUCING the outflow/water pressure to the house, EVEN when there is VERY LOW INFLOW(pressure coming in(to the reducer) from the MAIN (city water line), which is very common here(in Indonesia) unfortunately , which is exactly WHY I installed a Reducer(bcz pressure from main city water line is constantly UP&DOWN(either too high or too low!!).
    – Ben
    Oct 5 at 12:01
  • Have you adjusted the PRV? Counter clockwise or anti clockwise turns of the adjustment reduces the setting you should be able to turn the flow off or close by turning it . If it is set at a high value it won’t regulate, they can only reduce the pressure once it is above the set point.
    – Ed Beal
    Oct 5 at 13:35
  • I understand that, thnks but no, I don’t have it set that high(around 4bar), bcz since I installed the PRV, my small electric water heater’s overflow valve has been activating(dumping water, unlike ever before), even when I have lower pressure coming in than before(with a low PRV setting): all very strange, really!?!
    – Ben
    Oct 6 at 2:10
  • Perhaps, I should add that I still have a well-waterpump (pumping from a water collection tank) connected to the whole water system/lines like Ive always had since the beginning(bcz city water inflow was often not enough):could that somehow create a problem?
    – Ben
    Oct 6 at 2:42

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