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pulsating freshwater pump

Marine Plumbing

Section - Hi All, i have to update on my hatch installation project, but in the meantime, ...
   
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    Hi All,

    i have to update on my hatch installation project, but in the meantime, i replaced my freshwater pump.

    the old pump is a flojet, 3 gpm that wasn't giving me any water pressure. The new pump is also a flojet, but a little larger at 4 gpm.

    My challenge is everything seems to work, except when i turn on any of the taps, teh pump pulsates slowly between going and slowing down....about once every second. It does turn off when the taps are closed. I used it with the vacu flush toilet, and it added water then shut down no problem.

    one concern i have is the fittings on the new pump are 3/4", so i used fittings from the pump to fit a 1/2" line. is it possible a 1/2" line isn't letting it have enough water?

    Any ideas why it just doesn't run smoothly while the tap is open?

    cheers

  2. #2
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    Wow, I wouldn't think that the 1/2 line would be causing this problem. Just curious do you have the capability to wire the pump straight to a fully charged battery for testing then run it. I guess it could be the 1/2 line but I'm also thinking of an input water flow problem, or an electrical current to the pump problem.
    ~ on the hook ~

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    thanks Tim. Being we've been working on the electrical, that is a great suggestion. Maybe its not getting a solid punch of power....we'll test that today!

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    so the pump is getting power as needed.

    "pulsating"...the pump is basically turning on for a second, then off for a second.

    We notice the more we open the top, then less it does this, until the tap is wide open it doesn't do it at all. When we turn on the hotwater, it will pulsate, but cycle once only evey 8 to 10 seconds.

    our thought is the pump is working the way its supposed to. I'm wondering if the new 40psi pump is too big (the old pump was only 30psi).

    We talked about putting in a pressure tank but i don't really have the room....

    i guess the question is, Is the pump operating normally given the pressure it gives?

  5. #5
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    Well our pump is smaller and it doesn't do that, but it is certainly possible that it could normal for it to operate this way especially with a larger capacity pump. In other words if a system is designed for a 30 psi pump, when you open the tap the outflow will match the pump's capability and it will not be able to build residual pressure, but if you stick a 40 psi pump on it and the system cannot discharge as much as is being provided then the restricted flow will be at a higher pressure and could cause the pump's pressure switch to trigger turning the pump off until the pressure drops, then it comes back on. Still seems strange to me though, so I will continue to scratch my head on that one.

    My system has an accumulator on it to help smooth out the pressure spikes and my pump has a pressure switch that is in declining health....lol So I do have strange issues myself....hehe
    ~ on the hook ~

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    we were able to speak with the Flojet rep, and he told us that is what the problem is. The store let me exchange it for a 30psi pump. I've installed it and the system now runs smoothly and quietly! One more project done!

    AFter all this, i now believe the original problem was probably the filter not being installed correctly. I think the cap on the filter was not screwed down properly, letting air into it thus causing the percolating that we were seeing. I reconnected the old pump just for the heck of it, and it worked with the filter installed correctly. One more part to keep as a spare :-)
    Roger likes this.

  7. #7
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    glad you got it figured out, sometimes bigger is not better and I for one really hate admitting that.
    ~ on the hook ~

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