Water pump adjustment

[georgelesley]

We have a Shurflo 4008 bypass type pump that cycles on and off constantly no matter the flow rate demanded. The manual says the hi pressure setting might be too low. There is an adjustment on the pressure head.

Anyone ever do this, if so how sensitive is the adjustment, is the pump running to set it?

[BuckyBadger]

Don't know what your manual says but this is from the website

NOTE: By-pass adjustment should only
be performed by a professional technician
with proper gauges and equipment.


The by-pass is a spring loaded diaphragm
that opens up allowing water
from the discharge side back to the inlet
side. The by-pass is set to begin opening
at about 40 psi and creating full by-pass
at about 62 psi (lower pressure pumps
will vary depending on the by-pass and
pressure shut-off settings). The pressure
switch on the pump is set to shut
off at 55 psi. If the switch or by-pass
are adjusted too much, the by-pass and
switch shut-off can overlap and THE
PUMP WILL NOT SHUT OFF. Screwing the switch screw in clockwise will
raise the shut-off pressure. Unscrewing
the switch screw counterclockwise
will lower the pump shut-off pressure.
Screwing the by-pass screw in will raise
the pressure at which the by-pass starts
and raise the full by-pass pressure.
Unscrewing the by-pass screw counterclockwise
will lower the pressure at
which by-pass starts and lower the full
by-pass pressure.
WARNING: If full by-pass is reached
before the shut-off setting, the pump
will not shut off. Full by-pass pressure
setting should be at least 10 psi higher
than pump shut off pressure

http://shurflo.com/images/files/RV_Product_Manuals/Fresh-Water-Pumps/911-1008.pdf

[Dick_B]

Suggest you call Shurflo for the best info.