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Thread: suction side blockage

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    Join Date
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    suction side blockage

    I have a very complicated plumbing setup; I don't fully understand where all the connections come from and go to. I have had three pool guys come out to fix other stuff and the consensus was "**** if I know...give me $600 to run and air compressor through all the lines and map them"

    I was getting decent suction through the skimmer basket and spa drains but zero suction from the main drain. So I got a Baker Hydro Control Plate http://www.sears.com/shc/s/p_10153_1260 ... xMPTOYx026
    and started playing with that in the skimmer. It worked, briefly. I swam down to the main drain and felt great suction. Then the next time I turned the pump on, it wouldn't prime. Now when I run at max RPM, I get about 1/4 of the intake pipe filled (used to fill the whole basket). I can only build 4 psi across the filter (used to run 24 psi at this RPM). I have flow but not enough to vacuum with a hose. If I reduce RPM to 1500 (where I used to set my filtering speed) it starves the pump of water and turns off.

    The house/pool was a foreclosure swamp with 3' of rotting leaves in the bottom. Who knows what got sucked into the plumbing. I did find a screw that I lost and a BB in the pump basket. Now the water runs clear. So there is some flow getting through but not nearly as much as there used to be. I think the blockage is near the pump since when I divert suction to the spa drains, there is no change in the pressure or flowrate.

    Other evidence - backwashing or draining to waste causes the same low-flow condition, so I don't think the problem is on the return side.

    I need this problem fixed in the next 3 days - I'm going on vacation for 9 days and need to set the pump to run while I'm gone.

    Time to call a pool guy, or try to fix this myself? I know there are drain snakes and the Drain King. I have two 90-degree bends above ground and god knows what buried.
    25K gal IG plaster pool w/ spillover jacuzzi, 12 Gulf Solar coils (leaking/currently bypassed), ancient Raypak propane heater (rusted/currently bypassed), Pentair 001018 VS pump, 4.9 sq ft Triton II sand filter, Taylor K-2006 FAS-DPD kit

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    mas985's Avatar
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    Re: suction side blockage

    Quote Originally Posted by twd000
    I swam down to the main drain and felt great suction.
    That's a bad thing not a good thing. You should never feel strong suction from a main drain. Otherwise, you may be increasing entrapment risk.


    Then the next time I turned the pump on, it wouldn't prime.
    This is because you have increased the suction head buy redirecting the flow rate more to main drain. Again, a bad idea.


    Main drains really aren't designed to clean debris out of the bottom. They should only be used for increase circulation in the deep end and even that is not really necessary. The skimmers are the most important suction port in a pool system. You want to skim the surface of debris BEFORE the debris drops to the bottom. If you need to clean debris off the bottom, a suction/pressure/robot/manual cleaner is much more effective at doing that.
    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: suction side blockage

    Quote Originally Posted by mas985
    Quote Originally Posted by twd000
    I swam down to the main drain and felt great suction.
    That's a bad thing not a good thing. You should never feel strong suction from a main drain. Otherwise, you may be increasing entrapment risk.


    Then the next time I turned the pump on, it wouldn't prime.
    This is because you have increased the suction head buy redirecting the flow rate more to main drain. Again, a bad idea.


    Main drains really aren't designed to clean debris out of the bottom. They should only be used for increase circulation in the deep end and even that is not really necessary. The skimmers are the most important suction port in a pool system. You want to skim the surface of debris BEFORE the debris drops to the bottom. If you need to clean debris off the bottom, a suction/pressure/robot/manual cleaner is much more effective at doing that.
    I'm not too concerned about entrapment risk. My deep end is 10 feet deep, and it requires some serious effort (mask, fins, snorkel) for me to get down there to inspect it. The odds of any kids ever getting down there is slim to none.

    I would agree that the suction head was increased when I had the diverted plate installed. However I have since removed it and I'm only pulling through the skimmer and spa. And I'm still getting reduced flow.

    Any tips on clearing this blockage?
    25K gal IG plaster pool w/ spillover jacuzzi, 12 Gulf Solar coils (leaking/currently bypassed), ancient Raypak propane heater (rusted/currently bypassed), Pentair 001018 VS pump, 4.9 sq ft Triton II sand filter, Taylor K-2006 FAS-DPD kit

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    mas985's Avatar
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    Re: suction side blockage

    Another problem with using the main drain to clean up debris is that they can easily get clogged and/or the pipe back to the pump.

    You might try back flushing from the pump with a hose wrapped in a wet rag stuck into the pump inlet pipe. This can be done for the main drain through the skimmer.
    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: suction side blockage

    I tried pumping with a garden hose wrapped in a wet rag . Both from the skimmer and the pump inlet. No luck. The problem seems to be that it is only a partial blockage, not a full blockage. So there must be enough open pipe to allow the hose to flow freely while not building any backpressure to dislodge the clog.

    Any reason to think the Drain King bladder will work better? OR time to cal in the pros?
    25K gal IG plaster pool w/ spillover jacuzzi, 12 Gulf Solar coils (leaking/currently bypassed), ancient Raypak propane heater (rusted/currently bypassed), Pentair 001018 VS pump, 4.9 sq ft Triton II sand filter, Taylor K-2006 FAS-DPD kit

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    Re: suction side blockage

    I had low PSI readings once, and trouble priming, I feared a failing pump. What I found however was a pump blockage... of sorts. I have towering pine trees near my pool. Pine needles in the pool are a daily battle. Those rascals will find their way past baskets, and for some reason collect at the opening of my pump.

    My fix was turn the pump off, remove the pump basket, and reach down inside the pump intake hole and clear out all you can with your fingers. I'm really not sure the anatomy of a pump, so I don't quite know what I'm feeling in there, but pine needles like collecting there on my pump. Cleared them out and immediately got great suction back and PSI numbers rose back to normal. Worth checking.

    14,000 gallon rectangle vinyl pool. 4' depth throughout
    Hayward SP2605x7 3/4 HP pump and S-220T sand filter (23 GPM filter rate) with SP0714T multi-port valve.
    Inline chlorinator
    T104R pump timer

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    mas985's Avatar
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    Re: suction side blockage

    It would be a good idea to check the impeller first. If that is clear you can try the Drain King. Sometimes it works better than a hose but not always.
    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: suction side blockage

    Well, I fixed it, I guess. Tried the Drain King on the pump inlet side and the suction diverter valve side, started the pump, same problem. Tried the Drain King in the skimmer basket and ruptured the bladded since I could not insert it fully into the hole.

    Took apart the pump, impeller and diffuser were clean except for a few stray hairs and small leaves. Put it back together, started the pump, and it ran like a champ. 25 psi pressure across the filter at 3500 RPM. I was expecting a huge slug of leaves in the strainer basket, but there was very little.

    At this point, it was acting more like an air leak in the pump, but I find it hard to believe that coincided exactly with adding the main drain diverter plate.

    I guess I fixed it, but it's a disconcerting not understanding what the problem was...
    25K gal IG plaster pool w/ spillover jacuzzi, 12 Gulf Solar coils (leaking/currently bypassed), ancient Raypak propane heater (rusted/currently bypassed), Pentair 001018 VS pump, 4.9 sq ft Triton II sand filter, Taylor K-2006 FAS-DPD kit

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