Water pump pulsing

[Wavery]

Actually, it works even if the "Rubber" hose is full of water. It's the slight flexing of the hose. If you watch the hose coil, you can see it try to straighten under pressure then relax when the pump is off.

I did this many years ago on my yacht. The pump was very noisy without it and when I installed the hose, the noise went away.

[Rob Culver]

Originally Posted by Idaho Adventurer

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.

Hi Idaho,
Once you made the adjustment, did it eliminate the pulsing from other faucets besides the shower, even when there was low water flow?

[Idaho Adventurer]

Originally Posted by Rob Culver

Hi Idaho,
Once you made the adjustment, did it eliminate the pulsing from other faucets besides the shower, even when there was low water flow?

For the most part, yes. It will still pulse some if a faucet is only opened up a little. It's in the nature of those pumps to do that. You just don't want them pulsing when you have a faucet opened all the way. When that's happening, the water pressure surges causing a surge/pulse of hot/cold. That's what the adjustment can fix.

[Rob Culver]

Originally Posted by 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

I'd like to try this idea but where would be the ideal place to put the T without having to do much work to fit it in? Is there a spot on the underside somewhere? That would be about the only practical way I would think as you need space to put 25 foot of hose.

[Bill]

Originally Posted by Rob Culver

Once you made the adjustment, did it eliminate the pulsing from other faucets ... even when there was low water flow?

Originally Posted by Idaho Adventurer

It will still pulse some if a faucet is only opened up a little.

Hmm. Pulsing at low water flow is an indication that the pump's TURN-ON and SHUTOFF pressures are set too close together.

For illustration, if the SHUTOFF pressure is set to 50 PSI, and the TURN-ON pressure is set to 48 PSI, the pump will run the system pressure up to 50 PSI and then shut off. Then, if you crack open a faucet at low flow, the pump will start almost immediately because you don't have to use much water to drop the system pressure from 50 to 48 PSI. And then it will turn off almost immediately because it has to rise only from 48 to 50. This is pulsing.

On the other hand, if the SHUTOFF pressure is set 50 PSI, and the TURN-ON pressure is set to 20 PSI, and you open a faucet at low flow, it will take a while for the system pressure to drop all the way from 50 to 20 PSI. When it eventually does reach 20, the pump will start, and will run for a long time because it has raise the pressure all the way back to 50. This is normal operation, not pulsing.

Of course, if you set the TURN-ON pressure way too low, like 5 PSI, the system will still work, but flow at the end will be a dribble.

On most RV water pumps, the SHUT-OFF pressure is adjustable, and you would raise the pressure to increase the spread and minimize pulsing. On some pumps, the TURN-ON pressure is factory-set and not adjustable, and on others, the spread between TURN-ON and SHUTOFF is adjustable. I've had both. But in the absence of leaks, pulsing at low flow is almost always an indication of TURN-ON and SHUT-OFF settings too close together.

Bill

[Idaho Adventurer]

Sorry if what I said was confusing. What you're saying makes sense. I think the word "pulsing" is maybe the wrong term for what I meant. I was referring to the normal and slow pressure fluctuation that happens as the pump gradually kicks on and off when a faucet is only opened a little (such as when trying to conserve water). This is normal for these types of pumps. I suppose "pulsing" would be better defined as a more rapid on and off of the pump. Hopefully that helps clarify what I meant.

[Bill]

No issue, Idaho. You are right - in the manufacturers' trouble-shooting literature, "pulsing" usually refers to unusually rapid cycling, as opposed to more expected operation. But the concepts are the same. Good discussion.

Bill

[Wavery]

Originally Posted by Idaho Adventurer

Sorry if what I said was confusing. What you're saying makes sense. I think the word "pulsing" is maybe the wrong term for what I meant. I was referring to the normal and slow pressure fluctuation that happens as the pump gradually kicks on and off when a faucet is only opened a little (such as when trying to conserve water). This is normal for these types of pumps. I suppose "pulsing" would be better defined as a more rapid on and off of the pump. Hopefully that helps clarify what I meant.

What you are describing "could be" an air leak in the plumbing from the tank to the pump. Just the slightest amount of air being sucked into that line will cause rapid pumping.

Often times, it's just a matter of a loose clamp or a nut at the pump (intake side) that needs to be tightened.