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Bob F Bob F is offline
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Default Water pressure pump keeps turning on

On 6/5/2021 11:48 PM, dan wrote:
On Sat, 5 Jun 2021 20:50:47 -0700, Bob F wrote:
The pump could be running all the time if it cannot get up to the cutoff
pressure. This could cause it to overheat because water FLOW is the only
thing cooling it much, and can certainly soften plastic pipe parts. If
it can't pump, the motor energy heats the water in the pump.


This is probably what made the plastic plug pop out without stripping.

The pump could be wearing out, and just can't get to cutoff pressure
anymore.


I think it's not getting to cutoff pressure because I measured it more
closely and it took less than five minutes to go from 20psi to 52psi
but the pump wouldn't shut off.


What is your set cutoff pressure? Higher than 52? That would suggest the
pump is the problem. Otherwise, the pressure switch is not working
right. Take off the cover and see what it does.


Once off, the pressure remains for hours (overnight is no problem but half a
day with water use it what it took so it was only two manual pressure cycles
for the whole day today, with showers and washing dishes included).


The black metal plug will rust. Galvanized less so, and brass not at all.


Is this pump one of those that turns off based on low flow, not
pressure. The flow sensor goes out on these, which will result in
continuous running. I recently pick up a slightly used grundfos MQ3-45B,
and discovered this while researching the use of it.


I think I found the source of the hissing which seems to be an air flow on
the pipe that connects to the bottom of the pressure switch. That pipe I
thought might contain water since it comes off the top of the pump but it
likely contains air. It seems to be the pressure that the switch senses.


The pipe to the switch to the pump carries water pressure to the switch
to active it. If there is air coming out of it, that would be surprising
to me unless there is significant air leaking into the input side of the
pump to mix into the water being pumped. Any leak on it could affect the
switch sensing, but I would also expect it to leak water when the pump
is off, unless there is a check valve between the pump and the tank. If
there is a closed valve or other restriction near the pump on that pipe
that only allows very small flow, the air leak could be lowering the
pressure seen at the switch.

The hissing could be coming from an air bleed valve on the pipe from
pump the tank if there is air leakage on the input lines. Otherwise,
find and fix the leak to see if that is causing the problem.


It's way down at the floor level only an inch off the concrete so it's hard
to tell but I can put my hand there and feel a slight flow of air even as I
can't pinpoint the hissing due to the pump noise (it doesn't hiss with the
pump off).

What I might do tomorrow is buy a new pressure switch and see how that pipe
connects to it. Or, I may just tighten up the pipe fittings. I don't know
how these fail so I don't know what is the most likely to be successful.

I can post pictures but I have to sign up for imagur first I think.


The first thing I'd look at is the pressure switch.Turn off the power.
Most of the ones I've used have a little nut at the top. Remove that and
lift the top off, to inspect the mechanism and contacts. Look for two
contacts welded together. You can usually operate the switch mechanism
by pushing down or lifting up on the little metal plate the the bottom
of the big spring pushes against. The contacts should close when you
push down, and open when you lift up on that plate.