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Pressure Drop wierd effect

joejoe Member Posts: 39
Wallies know water. So this is not  a heating question exactly.

Is there a control I could put in our house water supply downstream  of  the 1"  takeoff for the lawn sprinkler system  [which is just after the meter]    for the purpose of softening  the effect of a sprinkler zone opening quickly.? Why? Well, the sudden pressure drop felt in the 3/4" house supply actually tugs open the Delta 17 pressure balance valve in the upstairs shower. The hot water starts running at a goodly trickle, for hours, at 4:30 AM. It's a waste and a source of mold. I mean this happens when the shower is not in use. It is at least 40 feet away from meter.

Valve is 3 years in service. It has had a slight drip. I will install all new cartridge parts tomorrow, which Delta very thoughtfully supplied.. But will not know result till Spring, of course. Odd thing. But it happens every time. The lawn system is just new this Fall. It has the usual pressure breaker [?] seen on all systems  at the foundation. Thank you for any ideas.   Joe


  • icesailoricesailor Member Posts: 7,265
    Water Hammer:

    You need a water hammer arrestor like a small well Extrol or a potable water one. You are probably on a municipal water system. There is a (EPA) required check valve in the water meter service to protect the system from back flow from your system. The water flowing develops momentum. When the quick acting valves in the irrigation system close, the water must instantly stop. The shock inside the pipes can generate tremendous momentary pressures. If you were on a private water system (Private Well), the well Extrol tank would take care of the problem. You can also have problems with dripping temperature/pressure relief valves on water heaters because when the water is heated and it expands, it has no place to go. If you ever notice that when you get up early in the AM and turn on a faucet for the first time, the pressure seems momentarily higher, and returns to normal, you have a expansion problem and need a tank.

    The tank can go anywhere but the best place for it is as close to the connection for the irrigation system or the water service where it comes into the house. It should go AFTER the meter.

    An Iffy DIY project. You need to know what you are doing. I'd say to call a Pro but not all "Pros's" understand the concept. Delta didn't.
  • joejoe Member Posts: 39
    Pressure Drop weird effect

          Thank you IceSailor. That is darn useful. First good logical answer I have received.

     Have you known of  this hammer effect of lawn irrigation valves on household pressure balance valves?  I.E. This is not a WAG, right. Although a very informed one.

        Okay then. Is there a sizing aspect here, or just use a small Extrol?

    Sort of a one or two gallon looking one?

    [ I have experience in piping and  bracket mounting on my basement walls].

  • Jamie HallJamie Hall Member Posts: 6,653
    There really isn't a sizing aspect...

    I'd go with the two gallon.  It's important that it be charged with something very close to your normal household water pressure, or it won't do the job you want it to.

    And yes -- almost any quick-acting valve can cause this kind of problem, either on opening (a pressure drop in the rest of the system) or closing (a spike).  Older water closet or urinal flush valves were particularly bad actors.

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-McClain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
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