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Thread: How do main drains work?

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    How do main drains work?

    Hey Guys, newbie here. See the two attached pics. The red arrows point to the 2 main drains. The yellow goes to my pump. I'm assuming that the green goes to the main drains? How does the suction get to the main drains if there is nothing to connect the yellow and green? Appreciate any help.
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    jjslinger's Avatar
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    Re: How do main drains work?

    I was perplexed by the same issue at first.

    There should be a thing that looks like a flying saucer that drops in that hole just above your arrows. On this flying saucer is an adjustable flap; if the flap is all the way closed, your skimmer is doing nothing and all the water going to your pump is forced through your main drains. If the flap is partially or fully open, then the water going to your pump is divided between your main drains and your skimmer. The usual recommendation is to start with the flap about half closed, and adjust from there.

    Don
    16K gal IG 16'x28' pebble since 2011; Pentair Easytouch; Sta-Rite Intellipro VS pump; Sta-Rite 400 sq. ft. cartridge (System 3); 6 Heliocol Solar Panels; Aquamatic Cover; Legend pressure-side cleaner with Hayward booster pump; TF100 Test Kit.

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    jjslinger's Avatar
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    Re: How do main drains work?

    I guess I should have mentioned that the "flying saucer" is actually a main drain diverter valve; there are pictures in the "Visual Encyclopedia of Equipment".

    Don
    16K gal IG 16'x28' pebble since 2011; Pentair Easytouch; Sta-Rite Intellipro VS pump; Sta-Rite 400 sq. ft. cartridge (System 3); 6 Heliocol Solar Panels; Aquamatic Cover; Legend pressure-side cleaner with Hayward booster pump; TF100 Test Kit.

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    mas985's Avatar
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    Re: How do main drains work?

    I leave my float valve (actual term for the flying saucer) out most of the time. I would rather have the better skimming action than drawing from the main drain with reduced skimming. The main drain really doesn't do much anyway.
    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: How do main drains work?

    Thanks guys, perfect!!

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    Re: How do main drains work?

    The green hole might connect to the main drains, it might be plugged, or it might go to an equalizer.

    How many lines go into the pump?

    Is there a 1.5-inch hole in the wall directly beneath the skimmer?

    Can you post a picture of the front of the pump?

    You could put a garden hose into the front hole to see if any water comes out of the main drains.

  7. Back To Top    #7

    Re: How do main drains work?

    James, Yes the green arrow goes to the two main drains. There is only one line going to the pump. I used the hose trick and yes water comes out of the main drains. Thanks for the help.

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