My well system has worked problem free for the past 11 years. It has a
submersible pump at 220' with a pressure switch of 30/50psi. When
full, the pipes hold the pressure without leakdown. But recently, the
instant the pump kicks on the pressure drops to 0 for a split second,
then back to 30 and rising. The 0 pressure is noticeable in a water
stream also, kind of like a burp.
My first thought was a check valve, but the water pressure is constant
when the pump is off. Unless the pump has it's own check valve? But
then everything happens so fast there's no time for the water column to
fall. The pressure tank precharge is ok. Any suggestions?
My first thought was the pressure tank too. The precharge (with all
the water drained from the tank) should be 28 with a cut-in at 30.
That way the bladder is still slightly compressed when the pump comes
on. I know you checked it, but I would double and triple check the
tank. For the pressure to drop to 0, the source of the pressure has
to dissapear momentarily, which sounds like a bladder running out of
travel to me.
If that's really OK then it might be a check valve. Deep well
submersible pump installations sometimes have several check valves
spaced along the pipe. If the lower one has failed and water drains
out of the pipe, it could take the well pump long enough to charge it
that the PT runs out of bladder travel anyway.
A third possibility is a pump problem such as a mostly plugged screen
or wear in the pump that causes it to take longer than it used to to
charge and pressurize the line, again causing the PT to drop out.
Double check the tank. If it's ok, then it's time to call the well
If your tank is not loosing pressure when not drawing water and your
precharge is correct - 28psi when the tank is empty, there is nothing
wrong there. If the pump is operating normally when it does start,
there is probably nothing wrong with it.
Having just been through the same thing with mine I traced it down to a
The 1/8" riser pipe to the pressure switch was blocked and it took a
bit before the switch sensed the pressure change. Pull the switch,
pull the pipe and ream it out. Odds are that is the problem. The
operation is not a major thing if you are comfortable with wiring. YOu
have to disconnect the wire(s) going to the switch. Be sure to note
the placement of the wires on the terminals. Other than that it is
just a matter of a small pipe wrench and possibly a drill bit to ream
the pipe with.
Thanks for the info - I'll try that. I decided it wasn't the pump
because it does the same thing with the power to the pump off. I
rechecked the precharge & it was 27lb. I slowly increased the pressure
up to 35 lb, checking at multiple points and it did the same thing,
just at different pressure points. Your post gives me something else
to check. I know those iron pipes have a tendancy to accumilate crud.
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