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I'm having a sprinkler system installed and the PSI meter in my garage went from 85 psi to about 105 psi. Is it expected that a sprinkler system increases water pressure to my house? If not, is adjusting the pressure release value a reasonable approach to fix it?

  • Lawn sprinklers I take it? – ThreePhaseEel Mar 3 '17 at 3:33
  • Is this pressure reading with the water running anywhere or with no flow? If the heating of water trapped in the sprinkler system is the mechanism for increased pressure, then immediately after briefly running each zone in turn the pressure should be lower and then increase with time as the trapped water would increase in temperature. – Jim Stewart Mar 3 '17 at 11:31
  • An even easier test would be if the pressure reading is elevated, run the water in the house anywhere, then shut off the flow. Is the pressure now reduced? – Jim Stewart Mar 3 '17 at 11:48
  • AFIK all irrigation systems have a check valve to prevent backflow into the supply system. This should prevent trapped water from exerting backpressure. Also isn't the water in the irrigation lines at 0 psig after the water is shut off? If the lines heat up, wouldn't water just dribble out the heads or orifaces? – Jim Stewart Mar 3 '17 at 11:52
  • @JimStewart, yes it depends on how the system is built. If there is an external feed line before the control valve it will be pressurized and subject to heating. – Trevor_G Mar 3 '17 at 14:38
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It can, if you live in a hot sunny climate and there is no one-way valve to the sprinkler system. Cold water in, or on their way to the sprinkler valves will be heated by the ground or sun, and expand will a little causing significant back pressure.

If you have ever left your garden hose filled with water with the hose bib shut off on a sunny day, then pulled the trigger on the hose end, you will see the same effect. Lots of water pressure.

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Sprinklers usually drop your pressure while on but other than that there should be no change in pressure. I am thinking of lawn sprinklers.

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