I have an 80 gallon pressure tank and my pressure switch is set to 52/72. When I try to fill a 250 gallon tank with a 3/4 garden hose, there’s an instant pressure drop when pressure hits 40 psi

I’m able to get about 50 gallons out when the pressure gauge hits 40, then it instantly jumps to 16 and stabilizes at 16

I measured the GPM @ 16psi to be 10 GPM off my 1 1/2 HP pump, so I don’t think it’s a water issue. Is there something wrong with my pressure switch or possible the tank pre charge?

  • Try partly closing the valve on the hose, until the pump can maintain pressure at whatever flow rate that equates to. And measure that flow rate.
    – Ecnerwal
    Commented Nov 14, 2022 at 21:27

1 Answer 1


If you have a bladder style pressure tank, the bladder is probably broken. They do wear out, probably new tank time, sorry!

  • The 50 gallons before it hits 40 says not. The pump isn't able to make pressure at flow is what I'm seeing from that description. The bladder pressure is set rather low (should be 49-50PSI rather than apparently about 40 PSI if the pressure switch is 52/72) though in all liklihood that better approach here would be to lower it to 30/50 with a 27-28 PSI precharge - but if the pump can't make more than 16 PSI with the taps open, it's a pump problem.
    – Ecnerwal
    Commented Nov 14, 2022 at 21:08
  • @Ecnerwal Hard to tell. All wells are different. I grew up around wells all my life and they are all unique. We really don't know enough about his setup to give better advice. It could be a low producing well. If the pump was properly installed it would turn off when the water level in the well got too low...which I don't think is happening, but it's a possibility, it could also be "sucking air" if the water level dropped below the pump...that's of course assuming it's a submersible pump. If an above ground pump, everything changes. We need to know a lot more from the OP. Commented Nov 14, 2022 at 22:30

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