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Thread: Pump Flow

  1. #1
    Jumbo
    Join Date
    Oct 2005
    Location
    Crooked River Ranch, OR.
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    998

    Pump Flow

    I just had a real eye opener happen to me and wanted to share it with the forum. A few days ago I re-plumbed my super falls pump on my old pond. It used to come through a bushing going from 3" to 2", then through a 2" "90", then through a 2" knife valve, then to the suction of the pump. I needed to re do the pump placement to make room so I went from the bushing to a swedge and then straight into the pump suction, eliminating the 90 and the valve. Man o man did this change ever increase the flow over my bio falls. It made a big difference. My wife who dosn't pay much attention to the pond asked me why the falls were bigger, so she even noticed it. I didn't think the piping on the suction side of a pump made much difference but boy was I wrong.
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  2. #2
    Jumbo
    Join Date
    Dec 2003
    Location
    SJ, CA
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    625
    the 90 elbow, dimension of the pipe and the length all add to something called 'head loss'. The height of the waterfall also add to that. For most pump, there is likely a flow rate chart over head-loss. some low head pump has limit on how much head loss it can sustain, in general, larger head loss means lower flow rate.

    stan

  3. #3
    Tategoi
    Join Date
    Jul 2005
    Location
    Fremont, CA
    Posts
    367
    Right on Stan, Very often the problem lies with pumps being used in a place they are not well designed for. Not that it's a bad pump, just that there probably is a better pump for that system.

    The 2" line is a start. It may be a long line with several turns so any added disruptions would be more noticable. Another problem can be the 90 positioned right at the pump. The normal vortexes that cause a fitting to add to the total head can also interfere with the volute entrance disturbing the balancing important to the impellor.

    A pump will work better if the entering line is a straight run for 10 times the diameter of the line. That normally doesn't show up because we usually operate with 2'/sec flow on the suction side. (also people don't have the reference this system had as the change was made.) 2'/sec is a very slow flow and the vortexes created don't have much of an impact.

  4. #4
    Daihonmei
    Join Date
    Dec 2003
    Posts
    5,198
    birdman...
    I consistently hear that centrifugal pumps are better at pushing water than pulling water....which would mean that the plumbing on the inflow side would be MORE important.

  5. #5
    Nisai Mike Mazur's Avatar
    Join Date
    Dec 2003
    Location
    Cedar grove, NJ USA
    Posts
    141
    a lot has to do with weather or not the pump is trying to lift the water to pump it, I replumbed last year with 3 inch inlet lines and moved the pump to wher I had flooded suction, the top of my leaf basket is 1 inch below the level of my pond surface level. Makes the pump self priming and also allows for the clearing of anything in the line while I clean the basket. The pump sideI have plumbed with 2 inch and have zero fittings in the whole system to the inlet of the filter system. No fittings on the inlet, none on the outlet, max flow went up a good bit and I'll never ahve to prime that thing again. Sequence 6k gph pump.
    " I'd rather a bottle in front of me than a frontal lobotomy "

  6. #6
    Jumbo
    Join Date
    Oct 2005
    Location
    Crooked River Ranch, OR.
    Posts
    998
    My pumps are also below water line Mike. About two feet infact. Makes life easy. I also like to use long sweep elec. conduit where ever possible. You can see the long sweeps from the pumps and the water line in my Vortex here.

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