Variable/low flow from Shur-flo freshwater pump

[msw3113]

I've only used the 10-year old freshwater pump (Shur-Flo 2088-422-144) one time to put antifreeze into the lines, and it seemed to function satisfactorily.

Today I tried to sanitize the system in preparation for a trip of some length.  Blew out all the lines, nearly-filled the freshwater tank and added bleach.  Turned on the pump, ran water in the shower and was pleased by the strength of flow.  For about 10 seconds, after which the flow deteriorated to a weak stream.  I turned off the shower spigot, the pump kept running for a minute or so then stopped, after which pressure seemed to return but for only seconds, then returned to a pathetic dribble.

I ran bleach-water from the freshwater tank through all of the faucets at the rate of about 2 cups per minute.  I then turned the outside shower to help drain the freshwater tank.  Alas, the low-point drain is flowing faster than any of the pump-assisted faucets. 

This can't be right.  It seems that the pump works to pressurize the system, but thereafter cannot maintain a flow.  This appears to be a straightforward system with no water softener or accumulator in the path. Should I be looking at a diaphragm kit, a new pump, some kind of valve, or something entirely different?

As always, I'm grateful for guidance. :-[

 

[darsben]

On mine there is a screen on the intake side of the pump. Could that be partially plugged?

 

[SpencerPJ]

Sounds like you might be sucking air into the system.  When you winterized, how did you put antifreeze into the lines?  Does it have a bypass hose?  Check all the connections.

 

[msw3113]

@Darsben:  A clogged intake screen is possible.  I was hoping to eliminate other causes before removing the pump, as it was installed before (and therefore behind) the rest of the plumbing and wiring connected to the docking station.  Would a clogged intake screen result in the symptoms described?

@SpencerPJ:  To add anti-freeze I used the clear anti-freeze hose that's attached to a 2-position valve.  That valve is in the non-siphon position.  (I could hear the pump drawing from the siphon hose when I turned the valve.)  I'll go check again.  Would extraneous air in the system result in the symptoms described?

 

[Gary RV_Wizard]

Either of those could cause the symptoms you reported.  Basically, the pump is unable to get enough water via its inlet to keep the flow up, but the small flow that gets through is enough to build up line pressure after several seconds.

 

[Rene T]

You may also be filling the water heater tank. This takes a little time using the pump.  Are you getting a lot of air out of the hot water faucets?

 

[msw3113]

@Rene T: That was my first thought, but I had the hot water tank bypassed.

@ Darsben and SpencerPJ:  I hope you took no offense: my question about your suggestions causing the symptoms was my ham-handed way of asking for the explanation Gary provided.  Now I understand.

A Google search for the intake filter yielded a picture that was similar to the equipment in our 5er.  I wrangled out the filter assembly (without having to remove the pump, whew), opened it up, and immediately found that the tube-shaped mesh screen had become gunked up.  With what, I don't know but it was unappetizing.  A few minutes with a toothbrush de-gunked the screen and within a few more minutes the components were reassembled, all connections in sight tightened, and Huzzah!  Houston, we have water pressure!  More toothbrush work on the aerator screens and all is well.  My faith in the on-board system is restored.  The pump makes a bit of noise which I may address later.  Right now it's kind of comforting.

My thanks to all for your suggestions.  Later I'll post photos and maybe a how-to because this was at least in my case, such an easy fix everyone ought to know how to do it.  Maybe they do and I'm the most recent to discover it.

 

[Rene T]

Good to hear that. Now onto the next problem and there will be more unfortunately. That's all part of the RV lifestyle.  :-[ :'(

 

[SpencerPJ]

Great to hear, the best fixes are the ones that don't cost much  )

 

[grashley]

I had a similar problem, and similar filter gunk!  Pump was bad, too.  Glad it worked for you.

TO OTHER READERS
This filter is generally mounted on the pump inlet.  It comes in several styles, but all can be removed for cleaning without removing the pump.  It is a good item to put on your annual cleaning and service list.  Gunk just happens!