Water Pump Question

The pump has a built-in check valve that's supposed to prevent back feeding. Sometimes it gets clogged with a bit of dirt or scale and doesn't seat properly.

Maybe you have a loose screw.... see the thread I posted just a few days ago ... has photos: click here.

IF the water pump is ON and your city water hooked up, depending on the city water PSI, the pump will probably run and if running may allow backflow. Next time check to see if your pump runs when left ON and the city water is connected and you open a faucet. BUT, the standard fix is to replace the Pump. Its check valve is not seating at times. OR you can install an additional check valve on the output side of the pump. Doug

Doug, I always appreciate your responses since they seem to get to the root of a topic with no BS. I have a new Shurflo 4048 pump that is cycling far more than I would think is proper. I see from the paperwork that there are adjustable bypass and pressure shut-off switches but can't really see them due to the installation position.

Can you say what tool, screwdriver, allen wrench, etc., is needed to make adjustments and which should be adjusted to overcome the cycling? Any insight will be helpful since unless I remove the pump for access I'll be working blind. Obviously I would prefer to make adjustments while connected rather than adjusting and reinstalling each time since the freeplay in the lines wouldn't allow any other approach.

Thanks in advance for any assistance you may be able to provide.

hipower wrote:
Doug, I always appreciate your responses since they seem to get to the root of a topic with no BS. I have a new Shurflo 4048 pump that is cycling far more than I would think is proper. I see from the paperwork that there are adjustable bypass and pressure shut-off switches but can't really see them due to the installation position.

Can you say what tool, screwdriver, allen wrench, etc., is needed to make adjustments and which should be adjusted to overcome the cycling? Any insight will be helpful since unless I remove the pump for access I'll be working blind. Obviously I would prefer to make adjustments while connected rather than adjusting and reinstalling each time since the freeplay in the lines wouldn't allow any other approach.

Thanks in advance for any assistance you may be able to provide.

1. Allen wrench is used
2. The factory default settings is rarely at fault
3. Never heard of Bypass switches. But, Pumps have evolved over the years. Usually if you have to adjust the pressure switch cut off, that means the switch is slightly defective.
4. Shurflo calls the Pressure switch a BYPASS switch now. Same thing. Doug

1) Allen wrench is a 5/64
2) Pump has a Pressure switch that controls when pump shuts off (55#)
3) Pump has a 'Bypass' Spring Loaded Diaphragm that begins Opening at 30# and is FULLY open at 65# (should not reach full open position)
4) Pressure Switch and Bypass Valve have their OWN adjustments
5) Clockwise adjustments raise Pressure Switch shut off set point (counter clockwise lowers)
6) Clockwise adjustments raise Bypass Diaphragm pressure point to begin opening/and pressure when it is fully open (Counter clockwise lowers opening & fully open pressure points)
7) 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.

With a Faucet WIDE Open the pump SHOULD run continuously (counter clockwise adjustment on pressure switch screw until pump runs smoothly)
Then close faucet down to half flow.....turn pressure switch adjustment counter clockwise 1/4 turn (out)
Then turn bypass valve adjustment screw counterclockwise (out)until pump runs smooth
Close faucet down to a trickle ----enough to rinse off a plate
Then turn bypass screw counter clockwise (out) 1/4 turn

Pump should run smooth full open faucet and with a slightly more then a trickle flow.
If pump doesn't shut down when faucet closed...turn bypass adjustment screw clockwise (in) until pump stops (small increments)

Dutch_12078 wrote:
The pump has a built-in check valve that's supposed to prevent back feeding. Sometimes it gets clogged with a bit of dirt or scale and doesn't seat properly.

This has happened to me 3 times in 6 years. Usually when it happens, I just use the fresh water tank for the remainder of the trip. By the next trip, things worked as normal.

Okay, my next question is if
"Pump has a 'Bypass' Spring Loaded Diaphragm that begins Opening at 30# and is FULLY open at 65# (should not reach full open position)"
the city water pressure is 45psi, what keeps the diaphram from opening(45psi>30psi) and filling the fresh water tank?

MetalGator wrote:

Dutch_12078 wrote:
The pump has a built-in check valve that's supposed to prevent back feeding. Sometimes it gets clogged with a bit of dirt or scale and doesn't seat properly.

This has happened to me 3 times in 6 years. Usually when it happens, I just use the fresh water tank for the remainder of the trip. By the next trip, things worked as normal.

If the water pump filter is installed and functioning there should be NO debris getting to the check valve. Doug

There may be a one way valve in the system someplace that's not closing properly other than in the pump.