System design description In an automated water main shutoff system, I have a downstream well pressure tank, hot water heater and softener past the main MOEN shutoff, which would have some water and pressure in it after shutoff event causing water to be able to be leaked further.

Background of what didn't work properly in system design Recent flooding event due to worker errors, which resulted in proper automatic shutoff the main (detecting water leak), but since they had both hot and cold water washer spigots open, with no hoses on at washer, since they were going to move it waiting for parts (2nd error). They thought the valve was closed (1st error), as there was no water when they turned the valves and removed the hoses. There was a frozen line upstream in the PEX line before the valve so it was blocking flow to these spigots when open, when the cold front moved on and it warmed up it melted the ice plug allowing 100 gallons+ water leak (detected by Moen flo detector at washer triggering closing of Moen main shutoff) after main shutoff position. I assume since main was shut off that this meant the water came from these other reservoirs.


  1. The question is after an automated shutoff; should I also have electrical shutoffs at each of these other appliances?
  2. How will the waining water pressure affect them?
  3. Will the pumps and heating elements handle these conditions?
  • How was it that water leaked (on the floor, I presume?) because the taps at the washer were open? Aren't they always open whether the system is pressurized or not? I don't see how one thing caused the other. Please edit to clarify.
    – FreeMan
    Feb 2 at 20:08
  • A drained electric hot water is not nice. The elements burn out. I think you want back flow preventer, simple valves that only let water flow in one direction.
    – crip659
    Feb 2 at 20:10
  • Updated structure to include components in system past shutoff; How the system failed to protect from downstream components releasing stored water and ultimately what Moen recommended as an adjustment (in Answer section). Rant section was for plumber who didn't know what he was doing on any front and who's collective errors helped to create the event in first place. Useful points as to elements that contributed to flood.
    – R Premo
    Feb 3 at 22:44

1 Answer 1


Moen Answer on changes to where shutoff is placed: After 3 emails to Moen support of shutoff valve they finally came back with a recommendation for the shutoff to be moved to behind the pressure tank. So this would also cut pressuring out the system. Moen Tech doc further explains https://solutions.moen.com/Smart_Water_Security_Products/Help_Center/FAQ%27s/Can_the_Flo_Smart_Water_Monitor_and_Shutoff_be_installed_on_any_type_of_water_supply_line%3F

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