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Thread: Pump not keeping prime on skimmer only - main drain works fine

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    Pump not keeping prime on skimmer only - main drain works fine

    Hello all,

    I found this site online a few months back and its been invaluable in terms of helping me learn how to maintain and enjoy my pool. A problem has now arisen that i need some help with.

    My pool has a diverter valve that lets me choose if I want suction on the main drain (bottom of pool) or the skimmer basket, or a combination of both. I have a lot of vacuuming to do so I've been vacuuming to waste running only the skimmer suction and a manual vacuum. Over the weekend i hit a pretty big patch of leaves and pulled them up into the pump area and since then i have been unable to maintain a good prime on the skimmer side.

    The main pool drain line (alone or in tandem with the skimmer) primes no problem - which makes it seem there could be a leak on the skimmer side. If I prime the pump using the main drain, then switch to the Skimmer, bubbles flood into the pump basket. Then it seems to struggle for awhile and the water level drops. Then it starts building up again and as soon as it seems that its about to prime, the water level drops again.

    There is only about 2 feet of above ground exposed pipe with 1 90 degree elbow and an adapter to the diverter valve. Nothing seems to be cracked, and I have yet to try running water over this part to try to see if the water is being sucked in (a trick I found on here).

    My question is would air coming into the system cause it to build up almost to a prime and then seem to lose suction?

    Thanks for any help or advice!!!

    -clink

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    mas985's Avatar
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    Re: Pump not keeping prime on skimmer only - main drain works fine

    I have a lot of vacuuming to do so I've been vacuuming to waste running only the skimmer suction and a manual vacuum. Over the weekend i hit a pretty big patch of leaves and pulled them up into the pump area and since then i have been unable to maintain a good prime on the skimmer side.
    This makes me think that you might have clog in the skimmer line. Have you tried back flushing the skimmer line with a hose and rag?

    Most any pump will leak air when the lines are clogged.
    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: Pump not keeping prime on skimmer only - main drain works fine

    Mark - thanks so much for the reply!

    I have not tried back flushing the line - is there a link that shows how to do that with a hose and rag (I apologize in advance if this is a stupid question). I was thinking of running to Home Depot for one of those bladder attachments to the hose if that would help...

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    mas985's Avatar
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    Re: Pump not keeping prime on skimmer only - main drain works fine

    You can use a drain king too. But the rag/hose method is basically the same. You use the rag wrapped around the hose to seal it into the pump pipe inlet so you can create pressure going toward the skimmer. Just make the valves are set for that skimmer only.
    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: Pump not keeping prime on skimmer only - main drain works fine

    Well I tried with the rag/hose and then got a drain king too - neither one worked. Water was coming back up through the skimmer line into the pool. Not a huge amount of pressure but enough so that you could see the pressure at the top of the water.

    Any other ideas? Thanks so much for the help!!!

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    mas985's Avatar
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    Re: Pump not keeping prime on skimmer only - main drain works fine

    When you switch from the main drain to the skimmer, does the filter pressure drop?
    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: Pump not keeping prime on skimmer only - main drain works fine

    Yes it does - at first it looks like "white" water flows in due to all of the bubbles when I switch from main drain to skimmer and the pressure drops and it seems to never build back up. Every now and again it will fill up almost to prime and then the pressure will drop again.

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    mas985's Avatar
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    Re: Pump not keeping prime on skimmer only - main drain works fine

    Are you sure the skimmer itself isn't sucking in air via a vortex?

    Is the pool level too low?
    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: Pump not keeping prime on skimmer only - main drain works fine

    Mark,

    Thanks so so so much for all of your help with this. You've been spot-on all along, but I think there was some user error on this end preventing the fix.

    Good news is - I did get it fixed. This morning I called a local pool company to set up a time for them to come out this afternoon to give me some time to work on it myself during the day. The tech asked what was happening and I told him, and I told him that I had tried your suggestions as well.

    So he offered to come out (to the tune of $75), but also gave me two suggestions to try as other ideas, the first of which worked.

    Basically since the pool drain side of the suction side worked, he said to get that side going (good seal and get the water flowing really good). Then on the top of the Jandy 3-way valve, loosen the top handle so that it could be raised above the post that normally keeps it from turning the pump pipe "off" so that i could move it into that position (essentially blocking the pump from getting water). When the water got to a point that it was really flowing, quickly turn the handle to block the pump, which would force the water to flow into the skimmer line and hopefully blow out any blockage there.

    It worked after the first try.

    The other option he offered (if I hadn't had that Jandy valve) was to insert a threaded pipe into the skimmer line that was high enough to raise above the water in the pool. Then quickly run the pump to clear any water in there, and fill that pipe with bleach/chlorine - which would, in theory, dissolve any organic material over a 24-48 hour period.

    The second option required a trip to Home Depot or somewhere like that so I tried the first which worked.

    Hopefully these tactics might help someone else with the same problem.

    But seriously Mark thanks so much for taking the time to help me with this issue - I really really appreciate it!

    -clink

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    mas985's Avatar
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    Re: Pump not keeping prime on skimmer only - main drain works fine

    While that method may have worked, it also creates water hammer (large pressure wave) which could possible damage the pipe/fitting joints. So I would always try the more benign methods before trying something that extreme.
    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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