Water pump pulsing

[Rob Culver]

Hello all,
When I turn a faucet on in my TM to a low trickle the water pump will pulse, i.e. turn on and off about once per second. The water flow rate itself though does not pulse. As I turn the faucet knob increasing the flow rate it starts pulsing faster and faster. At about half the maximum flow rate it stops pulsing and the pump just stays on.

My question is: Is this normal? I cleaned out the filter and that didn't seem to change anything. The Shurflo 4008 manual for the pump suggests that one cause for pulsing (or rapid cycling as they call it), is that the shut off pressure valve is set to low.

Unfortunately, the location of this shut off pressure valve is very close to the underside of the sink and getting a 5/64ths allen wrench in to a very tight spot is quite difficult.

Has anyone succeeded in actually adjusting this valve or the bypass valve in order to eliminate pulsing?

Thanks in advance....

[Shane826]

Yeah it’s normal. It turns on and off based on pressure. Runs for a second, pressurizes the plumbing even though there’s a trickle at the faucet, shuts off, trickle depletes pressure, pump pulses back on, lather, rinse, repeat.

When you get to about half throttle at the faucet the pump can’t pressurize the plumbing as fast as the water is flowing out of the faucet so it just stays on constant until you close the faucet then the pump runs a couple seconds longer until the plumbing is pressurized and then the pump shuts off.

[Rob Culver]

Originally Posted by Shane826

Yeah it’s normal. It turns on and off based on pressure. Runs for a second, pressurizes the plumbing even though there’s a trickle at the faucet, shuts off, trickle depletes pressure, pump pulses back on, lather, rinse, repeat.

When you get to about half throttle at the faucet the pump can’t pressurize the plumbing as fast as the water is flowing out of the faucet so it just stays on constant until you close the faucet then the pump runs a couple seconds longer until the plumbing is pressurized and then the pump shuts off.

Nice! Thanks Shane. I viewed the pulsing as a problem only if it was indicative of something going wrong. Glad to hear it's all good!

[Shane826]

If it keeps pulsing when the faucets are all shut off then you have a problem, you have a drippy plumbing issue causing a drop in pressure.

[Wavery]

If the pulsing bothers you, you can install an accumulator tank.

It can be installed anywhere in the waterline. It's a little cramped under the kitchen sink but it can be done.


"https://www.amazon.com/Akozon-Accumulator-Portable-Pressure-Waterproof/dp/B099K7SBGK/ref=sr_1_14_sspa?crid=2BT3G9TBWZ1HW&keywords=rv+ac cumulator+tank&qid=1706981948&sprefix=RV+Accumulat or+Tank%2Caps%2C189&sr=8-14-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9tdGY&psc=1

[Bill]

Wavery -

That is a good idea, but before embarking on it, take a look at this thread.

https://www.trailmanorowners.com/for...ht=accumulator

Note that this thread wobbles between fixing the pulsing and fixing the noise made by the pump when it is running. But apparently an accumulator that is small enough to fit under the sink is too small to do much good against the pulsing.

Bill

[Rob Culver]

Originally Posted by Bill

Wavery -

That is a good idea, but before embarking on it, take a look at this thread.

https://www.trailmanorowners.com/for...ad.php?t=15220

Note that this thread wobbles between fixing the pulsing and fixing the noise made by the pump when it is running. But apparently an accumulator that is small enough to fit under the sink is too small to do much good against the pulsing.

Bill

Thanks Bill, (and Waverly), for pointing me to the right threads. Hard to find alot of things unless you use the exact right search words.

[Idaho Adventurer]

Originally Posted by Rob Culver

Hello all,

Has anyone succeeded in actually adjusting this valve or the bypass valve in order to eliminate pulsing?

Thanks in advance....

I had to make this adjustment to mine last year because I installed a new low flow shower head, and even with the water on all the way, the pump would pulse on and off resulting in hot cold pulsing. I can't remember exactly how I got to the adjustment screw on the pump, but you're right in that it was very difficult to get adjusted do to being so tight of access under there. However, adjusting it solved my problem.

[Wavery]

Another trick is to get a 25' garden hose and "T" one end into your system somewhere. Cap the other end. This will act just like an accumulator tank. You just have to figure out where to put it. It can even be stored under the trailer somewhere.

[Bill]

That's a very inventive solution, Wayne. I like it. One thing, though. If the hose coil is permanently connected into the system (as a tank accumulator would be), and the coil is stashed below the level of the tee, drops of water will slowly migrate into the hose, "waterlogging" the hose/accumulator. Provision will likely need to be made to drain the hose every once in a while.

On the other hand, if the hose is permanently connected, and the coil is mounted above the level of the tee, or even stood up beside the connection, drops of water that enter the hose will drain back when the pressure is removed, and won't accumulate in the hose.

Or of course if you make the tee connection accessible, the hose coil could be connected and disconnected each time you set up and take down the trailer.

Bill