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Treetop Flyer · 07-12-2019, 04:23 PM

Recently replaced the water pump in our 2005 Winnebago Journey WKP32T with the new SHURFLO 4008-101-A65 revolution 12V RV water pump 3.0 GPM 12V. When using the shower or bathroom sink the pump rapidly pulses. The shower water volume is also less than desired. Operation is fine when using the kitchen sink. The pump strainer is new. All aerators are clean. Any ideas on why the pump rapidly pulses?

aknavy · 07-12-2019, 07:41 PM

You can add a accumulator/pressure tank to it that will reduce or eliminate the pulsing. Made a noticeable difference for us.

https://www.amazon.com/stores/node/2..._=fsclp_pl_s_7

Ray,IN · 07-12-2019, 08:26 PM

If the old pump ran normally, and the new pump cycles rapidly-with accompanying low flow, there is a restriction somewhere that was created during installation time-frame.

Gary RVRoamer · 07-13-2019, 11:13 AM

The pump cycles trying to keep up with the flow demand. The shower typically passes a lot more water than the kitchen faucet, though maybe if you opened the kitchen faucet fully it too would pulse.

One of two things has happened:

1.The new pump has a lower gallons/minute rating than the old one, or
2. There is some constriction at the pump inlet or outlet where you made the connection

This of course assumes assumes you didn't alter anything else when replacing the pump.

Old-Biscuit · 07-13-2019, 11:42 AM

Rapid pulsating of pump is due to pump discharge pressure reaching pump pressure switch STOP set point..pump shuts off. BUT shower is still on, system pressure immediately drops, low enough to cause pump pressure switch to close so pump STARTS. Then cycle repeats...Off/On/Off/On

Shower flow/demand is NOT enough to keep pump from cycling.
Remove the 'flow restrictor' in shower hose or handle to increase flow/demand when using shower. (some flow restrictors can NOT be removed....just use a 1/4" drill bit to enlarge them)

Adding a 2 gallon accumulator tank will help with the pulsating also.

To test my suggestion:
Turn on shower as if showering.......pump pulsating
Then open bathroom sink faucet just a little at a time until pump runs continuously.

Pump is Not the issue, nothing has been kinked/obstructed...just shower flow restriction.

Fiesta48 · 07-13-2019, 05:28 PM

If you read the manual there are 2 water pressure adjusting Allen screws. I've had to repair my pump several times. If the pressure is too low the pump cycles too often. Max pressure is 55 psi so it won't blow out piping.

Old-Biscuit · 07-13-2019, 05:49 PM

Quote:

Originally Posted by Fiesta48

If you read the manual there are 2 water pressure adjusting Allen screws. I've had to repair my pump several times. If the pressure is too low the pump cycles too often. Max pressure is 55 psi so it won't blow out piping.

Forgot about pump having a bypass diaphragm.
It starts opening at 40 psi pump discharge and is fully open at 62 psi
Pump pressure switch Start is 40 psi and Stop is 55 psi

Bypass should control low flow demands so pump doesn't cycle

If bypass and pressure switch stop set points are adjusted too much they can overlap and pump will not shut down.

Here is a down & dirty adjustment procedure for bypass & pressure switch
The Lazy Daze Companion: Adjusting The Shurflo Revolution 4008 Water Pump