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Thread: Not sure how my bottom drain works

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    Not sure how my bottom drain works

    Hello TFP - Great site, helped me with my swamp, but I still have a lingering question. How does my bottom drain work, and what is its purpose.

    Inside my skimmer, I have 1 hole which goes to the pump and another one (which had a gizmo in it) which I assume is connected to the bottom drain. What purpose does this serve?
    20,000 gallons
    In Ground Vinyl, Sand Filter
    Pool is older than 5 years

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    Richard320's Avatar
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    Re: Not sure how my bottom drain works

    Quote Originally Posted by macgyver89
    Hello TFP - Great site, helped me with my swamp, but I still have a lingering question. How does my bottom drain work, and what is its purpose.

    Inside my skimmer, I have 1 hole which goes to the pump and another one (which had a gizmo in it) which I assume is connected to the bottom drain. What purpose does this serve?
    Does the gizmo resemble this?


    That is a diverter. If the little flap underneath it is completely closed, the suction is directed virtually 100% to the main drain. If it's wide open, 100% skimmer. If the water level in the skimmer drops too low, the float inside the diverter drops and it draws from the main drain so you don't run the pump dry.

    It takes some experimenting to find the balance point for your pool. I watched the turbulence inside the skimmer without the diverter, then adjusted the door so there's just the slightest reduction in the skimmer. It worked out to just about halfway closed.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: Not sure how my bottom drain works

    That's a good idea. I didn't know they existed. Is any modification needed to my existing skimmer/basket setup? Are they standard sized? Do you just need it on one skimmer or both?
    +/-25K gallon L-shape vinyl liner inground
    sand filter
    Taylor FAS-DPD K-2006
    Polaris 360
    junior level BBB

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    Richard320's Avatar
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    Re: Not sure how my bottom drain works

    Quote Originally Posted by evanbone
    That's a good idea. I didn't know they existed. Is any modification needed to my existing skimmer/basket setup? Are they standard sized? Do you just need it on one skimmer or both?
    It depends on how your pool is plumbed. Some people have the second port blocked and a separate valve for the drain. I don't know about sizes. I measured my skimmer and went to the pool store and they had exactly one choice, but it would fit, so I bought it.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Mr. Blue's Avatar
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    Re: Not sure how my bottom drain works

    Richard, would you recommend adding one of these if not currently present?
    23K Gallon Freeform Tile Inground
    Hayward Super II 1.5 HP -- Pentair FNSP48 DE Filter @ 120 GPM
    Polaris 3900 Sport (with Booster Pump)


    Pool School Attendee -- The TF-100 Test Kit and the Pool Calculator keep my pool Trouble Free -- BBB Supporter

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    Re: Not sure how my bottom drain works

    So right now I do not have one of those, I just have 2 holes in the bottom of my skimmer, does that mean my bottom drain is not being used? And I second Mr. Blues question as well.
    20,000 gallons
    In Ground Vinyl, Sand Filter
    Pool is older than 5 years

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    Richard320's Avatar
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    Re: Not sure how my bottom drain works

    To answer two in one: yes, I recommend it. Without something to force the suction to draw from the drain, it won't. It's much easier to let the skimmer fill by gravity than to move it through a pipe. With some flow down low, it prevents temperature stratification. You had to have felt it somewhere before: you dip your toe in and it feels nice and warm, then jump in and hit ice water.

    Don't expect to feel any great suction down at the drain - if you have the required anti-entrapment covers you shouldn't. Brush a leaf or something towards the drain and see if it sits there or gets drawn in. Then you'll know. It also might be fun to check the water temperature on the heater before, and then check it again a minute or so after installing the diverter. I'm betting it will show cooler.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: Not sure how my bottom drain works

    i really have nothing to add except another question.

    my far skimmer doesn't seem to pull in the water as fast as the closer one, i mean sometimes debris just floats by instead of getting sucked in(i understand that some pressure might be lost because of the longer distance). so i was doing some reading and found that putting this skimmer diverter can help increase suction to the far skimmer. My question is should i leave the diverter open fully or close it half way? is it bad if i don't use the suction from the bottom drain? i am still pulling from the closer skimmer.
    27,000 gal. vinyl inground.
    Dyna glas 1.5H pump
    Triton II TR-100 sand filter
    Hayward C-500CF chemical feeder

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    Richard320's Avatar
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    Re: Not sure how my bottom drain works

    Quote Originally Posted by aviolentworld
    i really have nothing to add except another question.

    my far skimmer doesn't seem to pull in the water as fast as the closer one, i mean sometimes debris just floats by instead of getting sucked in(i understand that some pressure might be lost because of the longer distance). so i was doing some reading and found that putting this skimmer diverter can help increase suction to the far skimmer. My question is should i leave the diverter open fully or close it half way? is it bad if i don't use the suction from the bottom drain? i am still pulling from the closer skimmer.
    I'm not understanding how your pool is plumbed. The two skimmers are on one line? Or both skimmers and the main drain are all on one line?

    Actually, it doesn't matter. Just experiment to try and equalize the flow. If it turns out the diverter doesn't help, you're only out a few bucks.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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