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Thread: Strange pump noise...i'm baffled...

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    Strange pump noise...i'm baffled...

    Hi all

    My pump makes a strange noise and I am having a real problem diagnosing it - I am hoping TFP folks may be up for brainstorming with me!!

    As best as i can describe it, when it is (what I believe) "normal" sounding operation, the pump makes a clean, relatively high pitched sound. As clouds move over the solar panels, the motor rpm reduces as increases. This is because the pump runs directly off solar PV panels (through an MPPT controller).

    A few weeks ago we noticed that the pump noise will suddenly change, very occasionally with an associated "rattle" of the sand filter line connected to the pump. When the pump changes, the motor sound goes down an octave - again, as best as I can describe (attached video of lower octave sounding pump motor noise.https://vimeo.com/135932808

    When the pump changes sounds, i do not notice a change in flow or pressure. Also, we had the pump inspected and all seals were fine, and the bearings were fine - it was reported as being mechanically fine, with no debris or dog hair in the impeller. We also had, when we took the pump in for an inspection, a suction side leak - we had tried to patch it with silicone and plumbers wrap, which reduced the leak, but didn't eliminate it.

    The pump expert (nb, just a pump expert, not a pool guy), mentioned that the suction side leak could be the issue, causing cavitation, or something internal that moves back and forth in the motor housing. Today we repaired completely since the suction side leak. When i fired up the pump it ran normally, with a high frequency motor hum, for a few minutes, but then the pump started to make the sound intermittently, and after a short while, continued to operate continuously with that lower octave operating pump motor sound.

    Anyone with any best guesses? I'm running out of things to check, and baffled!

    Thanks for taking a crack!
    t




    68,000litee, IG vinyl, LorentzPS 600 Solar Pump & 1/2 HP Tristar, Sandfilter, Aquarite T-15 SWG
    20000 gallon, IG, SWG, Sand Filter, Hayward 1/2HP + Lorentz direct solsr PV pump

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    Re: Strange pump noise...i'm baffled...

    It's your suction side leak. There is an article in Pool School you may find helpful. If the noise change is consistently rhythmic your pool water level is probably too low (or the skimmer basket is chocked full) allowing the skimmer to suck air.

    There should be little to no air in you pump strainer basket.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Strange pump noise...i'm baffled...

    Suction side leak was repaired - whole new plumbing put in. I have also found that air can still remain in the basket if the pump is not powerful enough to displace all of the air - the best evidence of a suction side leak is not air in the strainer basket, but bubbles in the return jets. We also checked pool water level, which is fine as well...


    68,000litee, IG vinyl, LorentzPS 600 Solar Pump & 1/2 HP Tristar, Sandfilter, Aquarite T-15 SWG
    20000 gallon, IG, SWG, Sand Filter, Hayward 1/2HP + Lorentz direct solsr PV pump

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    Re: Strange pump noise...i'm baffled...

    I'm not a pool guy, but I know pumps, valves, and associated equipment. Is there a suction valve that isn't open all the way by chance? Perhaps one that appears to be open, but maybe isn't? Does there happen to be a suction pressure gage?

    Like mentioned above, it sounds like the pump is beginning to cavitate. Full blown cavitation will sound like marbles in a tin can.
    21' Revelation AGP ~10,500 gal, Pentair SD60 Sand Filter w/ 1 1/2 HP Dynamo Pump, TF-100 Kit
    Installed 07/25/2015 with city water.

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    Re: Strange pump noise...i'm baffled...

    the best evidence of a suction side leak is not air in the strainer basket, but bubbles in the return jets.
    Where does that air in the return jets originate? It doesn't start on the pressure side.

    Air originates from the suction side of your system and when you find that and fix it, I think all your issues will be solved.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Strange pump noise...i'm baffled...

    Since I no nothing about solar panel powered pumps, I'll throw out a dumb question. I assume the "MPPT" controller controls voltage and amperage to run AND protect pump. So if ALL suction side leaks are addressed, could low solar output (i.e. Cloudy skies) cause the pump to slow down enough to cause cavitation and thus air and associated noises ?
    Si -central Mo. 32' x 16' -- 3'4" to 6' deep Vinyl liner - 16,500 Gals : Triton II filter -Duraglass 2 hp pump - 1 speed : SI-30 salt generator
    TF-100 with speedstir

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    Re: Strange pump noise...i'm baffled...

    Cavitation doesn't fit...
    Suction cavitation occurs when the pump suction is under a low-pressure/high-vacuum condition where the liquid turns into a vapor at the eye of the pump impeller. This vapor is carried over to the discharge side of the pump, where it no longer sees vacuum and is compressed back into a liquid by the discharge pressure.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Strange pump noise...i'm baffled...

    There are no bubbles in the return jets any more...hence why i think we have eliminated the suction side leak


    68,000litee, IG vinyl, LorentzPS 600 Solar Pump & 1/2 HP Tristar, Sandfilter, Aquarite T-15 SWG
    20000 gallon, IG, SWG, Sand Filter, Hayward 1/2HP + Lorentz direct solsr PV pump

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    Re: Strange pump noise...i'm baffled...

    Quote Originally Posted by lefty51 View Post
    Since I no nothing about solar panel powered pumps, I'll throw out a dumb question. I assume the "MPPT" controller controls voltage and amperage to run AND protect pump. So if ALL suction side leaks are addressed, could low solar output (i.e. Cloudy skies) cause the pump to slow down enough to cause cavitation and thus air and associated noises ?
    We thought that originally, but it also occurs under full sun too. Your thinking on MPPT is quite accurate - which stands for "Maximum Power Point Tracking", which seeks to maximize output by finding the best voltage and amperage on the panels, based on the load (in this case, the 3-phase DC pump)


    68,000litee, IG vinyl, LorentzPS 600 Solar Pump & 1/2 HP Tristar, Sandfilter, Aquarite T-15 SWG
    20000 gallon, IG, SWG, Sand Filter, Hayward 1/2HP + Lorentz direct solsr PV pump

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    Re: Strange pump noise...i'm baffled...

    Thank you tlevy, see now you are teaching me. Isn't TFP wonderful
    Si -central Mo. 32' x 16' -- 3'4" to 6' deep Vinyl liner - 16,500 Gals : Triton II filter -Duraglass 2 hp pump - 1 speed : SI-30 salt generator
    TF-100 with speedstir

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    Re: Strange pump noise...i'm baffled...

    Do you get air when you bleed the filter?
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Strange pump noise...i'm baffled...

    Hmmm....how do i bleed the filter? I have never done that!


    68,000litre, IG vinyl, LorentzPS 600 Solar Pump & 1/2 HP Tristar, Sandfilter, Aquarite T-15 SWG
    20000 gallon, IG, SWG, Sand Filter, Hayward 1/2HP + Lorentz direct solsr PV pump

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    Re: Strange pump noise...i'm baffled...

    Quote Originally Posted by lefty51 View Post
    Thank you tlevy, see now you are teaching me. Isn't TFP wonderful
    My pleasure!!! Love TFP.


    68,000litre, IG vinyl, LorentzPS 600 Solar Pump & 1/2 HP Tristar, Sandfilter, Aquarite T-15 SWG
    20000 gallon, IG, SWG, Sand Filter, Hayward 1/2HP + Lorentz direct solsr PV pump

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    Re: Strange pump noise...i'm baffled...

    Anything causing unnecessary head loss to the pump?
    21' Revelation AGP ~10,500 gal, Pentair SD60 Sand Filter w/ 1 1/2 HP Dynamo Pump, TF-100 Kit
    Installed 07/25/2015 with city water.

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    Re: Strange pump noise...i'm baffled...

    Not to my knowledge. There are a few 90 degree elbows, but nothing beyond that. The sand filter shows about 12-14 psi...


    68,000litre, IG vinyl, LorentzPS 600 Solar Pump & 1/2 HP Tristar, Sandfilter, Aquarite T-15 SWG
    20000 gallon, IG, SWG, Sand Filter, Hayward 1/2HP + Lorentz direct solsr PV pump

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    Re: Strange pump noise...i'm baffled...

    Often attached to the psi gauge, there should be a round knob that partially unscrews and bleeds air from the filter. Makes it easier to prime and keeps the filter from holding air.temp_pressure relief.jpg
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Strange pump noise...i'm baffled...

    I am assuming the motor runs on DC without using any inverters?

    Have you had the panels checked out to make sure the line voltage is constant?

    Can you run the pump motor on an alternate energy source (i.e. power supply).
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Strange pump noise...i'm baffled...

    Line voltage varies with sun, which is cleaned up with the controller. That being said, it is worth checking it out. I can power the pump with a 48v battery but don't have one...


    68,000litre, IG vinyl, LorentzPS 600 Solar Pump & 1/2 HP Tristar, Sandfilter, Aquarite T-15 SWG
    20000 gallon, IG, SWG, Sand Filter, Hayward 1/2HP + Lorentz direct solsr PV pump

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    Re: Strange pump noise...i'm baffled...

    Would changing pipe diameter from a 2 in run, down to 1.5, and then back up to 2 in do anything?


    68,000litre, IG vinyl, LorentzPS 600 Solar Pump & 1/2 HP Tristar, Sandfilter, Aquarite T-15 SWG
    20000 gallon, IG, SWG, Sand Filter, Hayward 1/2HP + Lorentz direct solsr PV pump

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