Sputtering water pump has me baffled

[Claude]

I have a Shurflo #2088 (installed in 2015 by a previous owner) that has developed a problem that I cannot solve. As far as I can determine, there are no leaks in the system. When I run the cold water, the pump will sputter (on/off/on) when it delivers water. When I run the hot side, there is no sputtering. When I run the two simultaneously, there is no sputtering. Only on the cold side. I'm assuming that there is air somewhere in the system on the cold side, but can't isolate it. When not in use, the pump does not sputter or burp. City water is no problem. A previous owner installed a water filter under the sink on the cold side. Could this be the culprit?

I have checked and tightened all connections. The strainer is clear. I'm at a loss at what to do. I searched the forum and the web and cannot find information about this type of problem. Many thanks for your help.

Matt
'97 Concourse SE

[BobW9]

I don't see how it can be the pump itself, as it is inputting from the fresh water tank whether the cold or hot water is running, so it should be the same. Air or something in the cold water pipe between the pump and outlets has got to be the issue, it would seem.

Could you perhaps have a leak in the cold water drain valve? Or air trapped right up against it? On my concourse the drain valves are on the floor behind the driver's chair. It seems to me that if that valve isn't strong enough, maybe under pressure from the pump and moving water, a little water gets forced out over and over, creating a short loss of pressure each time, to stutter?

1) First look under the coach where the drain valves are and see if there is any water on the ground.

2) If not, try to open both drain valves, turn on the pump for 10 or 15 seconds to force water through everywhere, and then close the drain valves. That should flush out any air trapped right up against the valve(s). See if that helps.

That's about all the ideas I have off hand

[LosLaureles]

Change the cold water faucet cartridge

[sm350bl]

Could the water filter be slowing down the cold side enough to bounce the water pump off the pressure switch?

[chin_k]

I think sm350bl is most likely have the right guess so far. I will isolate each and every part of the plumbing and see if the sputtering is all cold side, with/without the filter (try to bypass it to take it out of equation), and/or the kitchen/toilet/outside faucet. Also check the water heater and see if it is full of air.... should not be the case, since you said the hot water side is good. You can by-pass the hot water heater with the right setting for the various valves on the back, and there is should be a red button on a water filter to bleed out the air after you change the filter cartridge. Also, put a water pressure gauge on the pipe and see if there is something unusual about when the cold water is turned on.

I assume the cold water flow is normal. If not, it can be caused by a restriction on the cold water side, but that is very, very unusual. The plumbing in our rig is relatively straightforward, so it should not be that complicated, if you do the troubleshooting systemically.

[Claude]

Many thanks to all who replied. The culprit indeed was (most likely) the water filter cartridge. I say "most likely" because there was a loop in the supply line between the cartridge and the faucet. I'm guessing that a previous owner saved a few $$ by using the line when the filter was retrofitted in, and since it was too long, they just made a loop. Don't know if that put enough resistance in the system to cause the pump to sputter but it's working fine now. I'll get a new filter and see if the problem was related to the cartridge or the loop. As the 4th owner of this rig, I'm still in the "discovery" mode of what previous folks have done to it.

As an aside, we just finished a 7800 mile journey and averaged 11.2 MPG. I was pleasantly surprised. It's a great rig for our needs.

Matt

[68camaro]

Hopefully your fix works, I did change out my pump recently and water flow soooo much better.
That must have been one heck of a trip over 7800 miles, these rigs really are pleasant to drive.