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I recently replaced my well pump because I was told by technician it was bad. I replaced with a 3hp sitting at 360’ underground. We also replace control box, 86 gallon pressure tank and 40/60 pressure switch. Now that this is all done our pressure is worse than it was before.

I have a couple of questions. Does the size of pressure switch matter to pump size? The one installed was for up to 2 hp, but I have a 3 HP motor in the ground.

Also if I decide to install a holding tank next to my pressure tank in basement and ad another inline pump should I place that before or after the pressure tank? I have multiple hydrants outside and am not sure how they are plumbed and if the go to the pressure tank before the hydrant or on separate runs.

Any info helps. Thanks in advance!!

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    We like it one question one answer, so split it and provide some pictures.
    – Traveler
    Jun 15, 2022 at 0:23
  • As for the holding tank question, see diy.stackexchange.com/a/14626/18078 (replace the "filled by artesian well" with "filled by a brand-new pump that shouldn't need this step" - in either case, holding tank pressure is zero, all house pressure comes from the pump from the holding tank. The pump you have would then be controlled by a float switch in the holding tank.
    – Ecnerwal
    Jun 15, 2022 at 2:17
  • 240, the gauge reads 2 psi when water running and never gets above 10 when water is off. I’m watering 120 head of cows day and night, system was flushed, and pressure was fine when crew left, well crews are booked out months around me for appointments and are not able to make it back until august I was told, since it is hot daily I need water for animals.. system was flushed as watched them do the work to learn more about the situation at hand. Jun 15, 2022 at 13:52
  • How long did the system work correctly between the pump crew leaving (when "pressure was fine") and pressure dropping to 2-10 PSI? Hours? Days? Weeks?
    – Ecnerwal
    Jun 16, 2022 at 1:59
  • You never actually specified the HP rating of the original pump, just the rating of the new pressure switch and the HP rating of the new pump. What was the original pump?
    – Ecnerwal
    Jun 16, 2022 at 2:40

2 Answers 2

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The pressure switch is either on or off. As others have said, if it's undersized (amp rating), it could be a hazard or wear out soon. A basic pump system consists of the submersible (in your case) pump, pipe, pressure tank, pressure switch, probably an electrical box that contains the start and run capacitors and obviously the asso. wiring and breaker. You probably knew that, ...just repeating it here for context.

You need to know EXACTLY what was installed...ie model numbers of the pump and capacitor (control) box. They need to be compatible. Next you need to verify it was wired correctly. If a 240volt pump is wired for 120 volts, that's terrible and will burn out the pump in short order.

I saw what your already spent on this (even though it was edited out by isherwood). I'd contact the company and assuming it's not just a guy with a truck, contact his boss and insist they get out there right away. That's a lot of money to spend for a new pump and installation, IMHO. While I realize you need the water, I'd turn off the pump to prevent damage until your problems can be properly diagnosed and fixed.

EDIT WITH MORE THOUGHTS: You replace a 2 hp pump with a 3 hp pump, that means more GPM. Do you know the production characteristics of the well? Can it produce enough to support the larger pump? You might be drawing it down to the point where the pump is "sucking air". Every well is different. You really need well/pump guys to do this sort of work, plumbers just generally aren't knowledgeable enough.

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The pressure isn't bad due to overloading the pressure switch contacts (assuming they are actually switching the pump - if they are switching a relay/contactor that's switching the pump, they may be very lightly loaded, but that is not the usual way. Depends what's in the control box.) If the pump is 3-phase (which is possible but not the most likely at that HP) it might well be using a contactor.

The contacts on the pressure switch will tend to burn out early and provide no pressure at all (or weld closed and not stop running) due to being undersized, but that's not your main issue causing "bad pressure" right now.

That's a lot of pump. Your comment cleared up that you in fact have 120 cows to water. Your comment also stated that the pressure was fine when the pump crew left. So, the system as installed was capable of doing the job, and at some unknown point in time after the pump crew left, something changed.

If this wasn't a one-man outfit and you didn't get the head (or most experienced) person on the job, you might request a visit from the head (or most experienced) person to see what your $12,000+ isn't doing, and figure out why before you add a holding tank and another pump to a system that may not need it.

If you shut the pump off for a while, and it can build pressure when switched back on after you do that, you might have insufficient water coming into the well. Not the option I'd reach for first, since you mention "were told the pump was bad" not "increased the size of the herd" as your reason for the change, so I'd expect similar daily water use even if the new pump could pump faster (though the specifics of pump curves get a lot more subtle than the size of the motor attached. Similar GPM at more pressure, more GPM at same pressure, more GPM at less pressure are all possible when comparing specific 2HP and 3 HP pumps.) So, if the new pump is set deeper than the old one was, it might need more power to deliver the same pressure at full drawdown, for instance.

If you shut it off for a while and the pressure is pretty much the same when you turn it back on, there might be a leak in the well piping - something cracked or otherwise failed. Perhaps your pitless adapter, if applicable, is not seated correctly, or had an o-ring blow out. If you listen at the well-head you may be able to hear it (if it's actually the in-well piping leaking) - so (one option) your pump would be pumping valiantly, and much of the water would be falling back down the well. Very little pressure would make it to your end point due to it simply leaking away instead.

Another option is that it's the out-of-well pipe leaking, in which case a wet spot might be expected along the route of the water line (and you might be pumping your well dry, too.) In that case you probably would not hear anything at the wellhead, and you might see pressure build a bit after shutting things down (if it's low due to pumping water into the leak, and the leak is not back into the well.) If you build whatever pressure you can build with the water shut off past the pressure tank, and then shut off the pump, pressure should hold steady. If it drops instead, that's a sign that something is leaking, though this can be complicated by the relative locations of any check valves and the pressure gauge(s)

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