We have a well pump with a pressure tank. On two separate occasions, the wife and kids were running the water outside, connected to a slip n slide type of thing, going down the slope next to our house.

On both occasions, over the course of running the hose outside, the pressure throughout the house, as well as outside, drops to much below normal. The well pump never turns on. If I wait about 15-20 minutes, the pump eventually turns on and restores the house to normal pressure.

The only theory I can come up with is this: as our water heater has no backflow preventer (sometimes we get warm water from the cold faucets in the house right after a high-flow event like flushing a toilet), I wonder if the hose outside is actually creating a siphon effect within the house plumbing, perhaps causing a vacuum somewhere downstream of the pressure switch, maybe in the water heater itself. Since the pump doesn't come on, I have to assume the pressure on the switch side is high enough to keep the pump off. I also have to assume that the pressure switch and well pump are working correctly since 99% of the time, the water pressure is correct, while doing dishes, showering, etc.

Now to the question: given all of this information, is it worth putting in some sort of one-way valve on the cold side of the water heater? If not, what the heck is going on?

  • I would definitely put in backflow preventer(s) regardless of other problems. Dumping heated water into the cold side is expensive if nothing else. Meanwhile: what happens if you run the outside hose and run, say, your bath/shower? – Carl Witthoft Apr 8 at 17:46

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