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Thread: Main Drain Suction

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    NFLJACK's Avatar
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    Main Drain Suction

    When I dive to the bottom of the pool, I don't feel any suction in the main drain -- nothing. Is something wrong?

    Thanks.

    Jack
    Jack
    33,000 g, IG, , rectangle, 20 ft. x 40 ft., vinyl, Hayward pump and filter (will find out the models), cartridge filter, test kit: Taylor K-1004
    I'm not mad at the pool. I'm mad at the dirt.

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    Mod Squad jblizzle's Avatar
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    Re: Main Drain Suction

    Welcome to TFP!!!

    That is pretty typical ... they are designed that way to prevent entrapment. Of course whether you have flow through there or not is dependent on your plumbing and valving.
    Jason, TFP Moderator
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    Richard320's Avatar
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    Re: Main Drain Suction

    Hi, Jack!

    That's pretty typical. Even when I have mine on full, it doesn't feel like anything.

    Do you have a valve to open and close the main drain? If not, do you have two holes in the bottom of the skimmer?
    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: Main Drain Suction

    i just tested my own main drain over this same concern. I thought perhaps the skimmer/main drain ratio valve was installed wrong. But after moving it full one way and putting my hand in the bottom of the skimmer, under the venturi return, and then full the other way and having no suction in the skimmer, it's clear the valve is correct. I also folded up a bouganvillea leaf (no chance I spelled that right) and shoved it through the main drain grid. Got out of the pool and looked in the filter that is just before the pump and the leaf was in there.

    However, I can see a bunch of sediment accumulated in the ring of the main drain; the suction isn't strong enough to actually carry it around into the input ports of the drain. I'll probably have to get a vac attachment down there every once in a while to clean it out.
    10,500 gal IG, Topaz Pebble, auto-level
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    NFLJACK's Avatar
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    Re: Main Drain Suction

    Quote Originally Posted by Richard320 View Post
    Hi, Jack! :wave:

    That's pretty typical. Even when I have mine on full, it doesn't feel like anything.

    Do you have a valve to open and close the main drain? If not, do you have two holes in the bottom of the skimmer?

    Thanks for the responses.

    Yes, there is a valve where I can cut off either the skimmer or the main drain. I cut off the skimmer when I felt for the suction on the main drain.

    In the skimmer, there are two holes; however, one is plugged up with some sort of cap.

    Perhaps I'll take a colored leaf and poke it in and see what happens.

    Thanks.

    Jack
    Jack
    33,000 g, IG, , rectangle, 20 ft. x 40 ft., vinyl, Hayward pump and filter (will find out the models), cartridge filter, test kit: Taylor K-1004
    I'm not mad at the pool. I'm mad at the dirt.

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    Richard320's Avatar
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    Re: Main Drain Suction

    Quote Originally Posted by NFLJACK View Post
    Thanks for the responses.

    Yes, there is a valve where I can cut off either the skimmer or the main drain. I cut off the skimmer when I felt for the suction on the main drain.

    In the skimmer, there are two holes; however, one is plugged up with some sort of cap.

    Perhaps I'll take a colored leaf and poke it in and see what happens.

    Thanks.

    Jack
    Other ways to test it are: swim down with a bottle of food coloring and see if it gets sucked in. Or switch to full main drain suction and set a rubber mat or something over it and see if it starves the pump and the return pressure drops to nothing.
    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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