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Thread: Dynamo pump acting up (maybe)

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    moze229's Avatar
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    Dynamo pump acting up (maybe)

    Hello all, and happy freakishly early pool opening season this year.

    Short story - Dynamo 1.5HP Dual speed pump on .75 (low setting) will not pump freely or as much as it should. Backwashing helps initially, then goes back to not wanting to push the water as much as it should. The pump reservoir (the pre-filter after the skimmer) was full last year when the pump was running at 1/2 power. (You know how you can sort of see the water sloshing around at the clear lid?) Now what happens is that over time, you can observe the water level in the pre-filter at the pump drop where the water level is barely at the intake line. Pump on full power works like a champ.

    I just saw another thread that seems to have the same problem but mine is not that bad. In the other thread, the pump was just humming while sitting there and doing nothing. Mine sounds normal, it's just not doing what it's supposed to be doing. It's like it's loosing it's prime, but not all of the way.

    Pump worked wonderfully for the whole one month that I had it running last year before shut down. (We had the pool installed near the middle of September.) So, the filter media is new, the pump is new, and backwashing seems to temporarily fix the problem. This tells me that I may have something clogging the filter, but I'm not so sure. When I run the pump at full power, I'm getting 10 PSI at the filter. (Normal from what I've read.) When the filter is on low power, I'm reading 0 PSI, which is what it's always done. Now if I had clogged media, wouldn't I get at least SOMETHING for a PSI reading even on low? There should be some indication of resistance of water flow if there was a clog, but there isn't.

    Any ideas on what steps to take on this would be greatly appreciated. I suppose it's always possible to have a defective pump.
    24' X 54" Sharkline Matrix AGP ~ 15,200 gallon
    1.5 HP Dynamo Dual Speed ran 24/7 at low speed w/250lb. SD60 Pentair Sand Filter
    Plumbed with PVC - buried.

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    JasonLion's Avatar
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    Re: Dynamo pump acting up (maybe)

    That sounds like a suction side air leak. The first place to look is the pump strainer basket lid. The lid needs to fit securely and the sealing gasket should be clean and free of nicks. Another possibility is if the water level is too low in the skimmer, allowing air to be drawn in. And, of course, there might be a small leak in the plumbing on the suction side.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Mod Squad Bama Rambler's Avatar
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    Re: Dynamo pump acting up (maybe)

    Since you just came out of winterization I would also check the drain plug(s). And any other part on the suction side that got removed and reinstalled.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    moze229's Avatar
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    Re: Dynamo pump acting up (maybe)

    Quote Originally Posted by JasonLion
    That sounds like a suction side air leak. The first place to look is the pump strainer basket lid. The lid needs to fit securely and the sealing gasket should be clean and free of nicks.
    I'll check that. I didn't think of that.

    Quote Originally Posted by JasonLion
    Another possibility is if the water level is too low in the skimmer, allowing air to be drawn in.
    I don't think that's the case. I've checked that over and over and even checked for the "whirlpool" effect. Everything in this arena seems fine.

    Quote Originally Posted by JasonLion
    And, of course, there might be a small leak in the plumbing on the suction side.
    This scares me because 80% of my plumbing is buried 12" under. There are no leaks visibly, unless it's possible for air to enter the lines without having any water come out.

    Hopefully it's just the strainer lid as you said.
    24' X 54" Sharkline Matrix AGP ~ 15,200 gallon
    1.5 HP Dynamo Dual Speed ran 24/7 at low speed w/250lb. SD60 Pentair Sand Filter
    Plumbed with PVC - buried.

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    moze229's Avatar
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    Re: Dynamo pump acting up (maybe)

    Quote Originally Posted by Bama Rambler
    Since you just came out of winterization I would also check the drain plug(s). And any other part on the suction side that got removed and reinstalled.
    I'm going to recheck everything. The drain plugs have been reinstalled and there are no water leaks, so I just assume that they are fine. However, I did notice that Pentair sends the pump with the drain plugs installed with silicone around the plugs. I assumed that they did that to keep the plugs from falling out during transport more than anything. Is it possible to have an air leak and not have a water leak at the same time?
    24' X 54" Sharkline Matrix AGP ~ 15,200 gallon
    1.5 HP Dynamo Dual Speed ran 24/7 at low speed w/250lb. SD60 Pentair Sand Filter
    Plumbed with PVC - buried.

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    Mod Squad Bama Rambler's Avatar
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    Re: Dynamo pump acting up (maybe)

    It's very possible to have an air leak and not have water leak out. It happens all the time here. It's also common for the drain plug(s) to leak.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    moze229's Avatar
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    Re: Dynamo pump acting up (maybe)

    Ok. I think I figured out what the problem was. When I tell everyone I'm probably going to get a slap in the head.

    Contemplating the possible issue, one thing that I neglected to check was the strainer in the pump basket. The thing was filled to the brim! I've had a lot of junk in my skimmer from falling tree bud shells and I guess when I was emptying that the leftovers made their way into the strainer basket. Duh. I emptied that basket and everything seems fine for now. I'll know for sure when I check it in the morning. It's been on for about 5 hours now with no head loss.
    24' X 54" Sharkline Matrix AGP ~ 15,200 gallon
    1.5 HP Dynamo Dual Speed ran 24/7 at low speed w/250lb. SD60 Pentair Sand Filter
    Plumbed with PVC - buried.

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    Re: Dynamo pump acting up (maybe)

    I live in a forest - I know well of what you speak - I always have to keep checking my skimmer / strainer in the spring and I would in the fall if I didn't close my pool before the leaves started falling.

    I'm thinking seriously of opening my pool this weekend also....
    16x32 IG 19,000 gallons, Pentair 1.5 hp Energy Efficient Superflo pump (348024),vinyl liner, Chlorine dispenser, Hayward S-244T sand filter

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    moze229's Avatar
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    Re: Dynamo pump acting up (maybe)

    Quote Originally Posted by scooperhsd
    I live in a forest - I know well of what you speak - I always have to keep checking my skimmer / strainer in the spring and I would in the fall if I didn't close my pool before the leaves started falling.

    I'm thinking seriously of opening my pool this weekend also....
    I live in the woods also. Well, it's in a subdivision but we have a four acre lot. Most of it is trees. I've got some big ones out there.

    Being in Youngsville, I figured you would have opened up already with the warm temps already this year. I wouldn't have opened mine yet because we likely are still a while away from swimming, but I was concerned about the water turning green before I even opened up. The water in the pool is getting pretty warm already considering.
    24' X 54" Sharkline Matrix AGP ~ 15,200 gallon
    1.5 HP Dynamo Dual Speed ran 24/7 at low speed w/250lb. SD60 Pentair Sand Filter
    Plumbed with PVC - buried.

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    Re: Dynamo pump acting up (maybe)

    Success ! I got the pool cover off without dumping a large quantity of leaf material into the pool ! First time we have ever managed that. The whole secret was to keep sweeping the leaves all winter and use the cover pump to get as much water out as possible before pulling it off.
    16x32 IG 19,000 gallons, Pentair 1.5 hp Energy Efficient Superflo pump (348024),vinyl liner, Chlorine dispenser, Hayward S-244T sand filter

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