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Old 11-02-2015, 01:19 PM   #1
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Low Water Pump Pressure

Hey gang,
I've been experiencing low water pressure on my bus since I finished it this summer. Ive tried replacing the pump, and all my connections/tubing is 1/2".

When Im connected to city water, I get awesome pressure and all flows well.

When Im boondocking, I get great pressure for the first 3-5 seconds, then I have very little pressure, showering sucks and there's no way Im getting the 3.xgpm that shurflow specs the pump to. This happens with either hot or cold, and on all my faucets.

Here's a video of the problem I made:



What the heck can I do to fix this?!
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Old 11-02-2015, 02:32 PM   #2
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check the tank for an obstruction.....

im guessing it pumps all the water in the pipes and accumulator fine, but cant refill the system fast enough. try 3/4 " pex to the pump maybe, maybe the pex line is pinched between the tank and accumulator.

3.5 gpm pump should push a single faucet fine.
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Old 11-02-2015, 02:53 PM   #3
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Ive actually already checked the tank for obstructions, and the hoses to and from the pump are the 1/2" ID flexible lines that I purchased from shurflow specifically for mounting this pump.

Im stumped!
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Old 11-02-2015, 03:32 PM   #4
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There isn't a mention in the video about how the city water connection is made, so I'll assume it's a tee somewhere after the accumulator, and that it all relies on the built-in check valves in the city water connector and pump. This and the decaying pressure and long pump cycle after closing the valve make it look like the accumulator and all else downstream are fine, as turf suggested and you probably already knew.

You could probe its supply wires while the pump runs to be sure there isn't excessive voltage drop causing the pump to run slow. This seems unlikely because the pump sounded like it's running fine, but maybe worth the few seconds to verify anyway.

Seems like a water supply problem. Is the suction line collapsing anywhere? Is the filter unit directional and possibly installed backward?

Try using a short piece of tube to draw water from a bucket on the floor directly into the pump, bypassing the screen/filter. If it pumps fine from there move the bucket and tube upstream toward the tank incrementally until you find the obstruction.
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Old 11-02-2015, 04:25 PM   #5
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Pump voltages are good--right around 13v.

I haven't tried putting the pickup tube in a bucket, next time my tank is empty Ill pull the line and put it in a bucket.

I wonder if there is a pinhole leak in my hose coming from the tank to the pump causing the pump to get air bubbles.

And yes, the city water connection is a tee that happens after the pump/accumulator.

I think the next steps are determining if the issue is beforw or after the pump
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Old 11-02-2015, 04:44 PM   #6
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Charles, I put your issue to the folks at irv2 and so far;

"It appears as his system is pressurizing but then after the faucet is turned on there is no flow. On my Shurflo pump there are screens on the intake side, you may have your friend check to see if these screens are plugged. A plugged screen would allow the system to pressurize but once you try to run water would not provide the volume you need."
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Old 11-02-2015, 04:49 PM   #7
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The pinhole leak theory is interesting.

I meant to suggest a new piece of sold-by-the-foot hardware store tube -- just the basic clear vinyl stuff with the braided reinforcement seems good enough for my pump. In suction use it doesn't collapse as easily as the unreinforced vinyl does. With a short alternate piece of tube for this experiment you can avoid questions about pinhole leaks, tube collapse, obstruction stuck inside the tube, or excess length.
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Old 11-02-2015, 06:06 PM   #8
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is the water level in the tank sufficiently higher than the pump? if you don't have a self priming pump and rely on gravity to fill, you might have some air trapped in there.

i cant pump out the bottom 3" of my tanks because of the height of the pump.
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Old 11-02-2015, 07:22 PM   #9
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Another: "I agree that the problem is from the pump back to the tank. To test, run a temporary hose from the pump into a bucket of water. If that works, blow out, clean or replace the line back to the tank. "
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Old 11-02-2015, 08:14 PM   #10
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Pumping into a bucket is nothing like pumping pressure through a shower head.

My pump will have a pressure gauge after the pump for diagnostic purposes.

Braided vinyl hose is garbage. Everywhere I have ever used it becomes a leak in less than a year. If you need a flex line between the pex and the pump, use a stainless flex hose like used on faucets and toilets.

I just watched your video. That almost looks like voltage sag. Does the pump sound like it's slowing down as the pressure drops?

Nat
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