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Thread: Help Making Sense of Bottom Return/Main Drain

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    njboater74's Avatar
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    Help Making Sense of Bottom Return/Main Drain

    Hi Everyone,

    I bought a house with an inground pool 2 years ago, and for the most part, I think I understand the equipment around the pool.

    One thing I'm most confused about is the main drain/return (shown below). I had a local pool professional out last year to close the pool, and he mentioned that the main drain wasn't hooked up. I think he was attempting to lower the water using the main drain, and had to use his own pump instead. I wish I asked more detail at the time, but it didn't really occur to me to ask what that meant.

    main_drain.jpg

    When the pump is running, it does return water, along with a single wall return in the shallow end.

    I have never witnessed it appear to take in water. But I don't know if I've ever truly isolated the drain to see if it can. Below is the valve for the intakes:
    return_valve.jpg

    The pool has two skimmers (1 at the shallow end and 1 at the deep end). Both are functioning properly at this setting. I can switch the valves to verify that both of them can take in water independently.

    So here are my questions:
    1. If the main drain/return were actually functioning as a drain, would I see another port in this valve for the drain?
    2. Could the main drain be connected to the same port as one of the skimmers?
    3. Is there a way to isolate the main drain to see if it's actually connected to work as a drain?
    4. Do dual purpose fixtures (main drain/bottom return) actually exist? or am i confusing the two?

    I'm really looking to determine what this fixture does (whether a main drain, bottom return, or both) and if it can function as a main drain, is it broken? or was it never hooked up that way?

    Thanks in advance!

    Dave
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    33k gallon, 40x20 IG Vinyl, Hayward sand filter, Hayward pump
    Hayward multiport valve, TF-100 Test Kit.

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    Mod Squad jblizzle's Avatar
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    Re: Help Making Sense of Bottom Return/Main Drain

    So is the valve in the picture for selecting each skimmer?

    1/2. Look in the bottom on the skimmer. If you see 2 open ports in 1, then that could be where the floor is plumbed in to.
    3. If it is plumbed to the bottom of a skimmer, then a float diverter can be used to pseudo-isolate the floor drain.
    4. I think I have heard of them, but not sure I see the point.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
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    njboater74's Avatar
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    Re: Help Making Sense of Bottom Return/Main Drain

    Thanks for the prompt reply.

    Yes, that valve is for selecting each skimmer.

    I don't think there are two open ports, but am not sure what that hole with the square knob on it is:

    Deep-end Skimmer
    deepend_skimmer.jpg



    shallow end skimmer
    shallowend_skimmer.jpg
    33k gallon, 40x20 IG Vinyl, Hayward sand filter, Hayward pump
    Hayward multiport valve, TF-100 Test Kit.

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    Pool Tool's Avatar
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    Re: Help Making Sense of Bottom Return/Main Drain

    The square knob is the top of a pvc plug that closes off that hole, i.e. neither skimmer is connected to the main drain (in a typical manner anyway).

    "I can switch the valves to verify that both of them can take in water independently." This is confusing me - have you done this? When you turn the valve does one skimmer stop sucking while the other keeps pulling water?
    16' x 32' (21100 gal), vinyl, 1.5 hp Hayward SuperPump,
    Tagelus TA60/60D Sand Filter, Raypak 399K Digital Heater, TF-100

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    njboater74's Avatar
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    Re: Help Making Sense of Bottom Return/Main Drain

    Quote Originally Posted by Pool Tool View Post

    "I can switch the valves to verify that both of them can take in water independently." This is confusing me - have you done this? When you turn the valve does one skimmer stop sucking while the other keeps pulling water?
    Sorry for the confusion. Yes, when I turn the valve, one of the skimmers stops while the other keeps pulling water. This works for both skimmers. Thanks for your answer.
    33k gallon, 40x20 IG Vinyl, Hayward sand filter, Hayward pump
    Hayward multiport valve, TF-100 Test Kit.

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    Mod Squad jblizzle's Avatar
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    Re: Help Making Sense of Bottom Return/Main Drain

    So the floor might be plumbed to the bottom of one of those skimmers. And then either the plug was left in after a closing accidentally, or it was plugged up due to a leak in the floor drain plumbing.

    You might need to get down on the bottom and pull the drain cover to see if it is plugged down there too.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
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    Pool Tool's Avatar
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    Re: Help Making Sense of Bottom Return/Main Drain

    So it could be that the piping to one of the skimmers is tied into the main drain directly rather than via the other hole in the skimmer or is just accidentally plugged like Jason mentioned. One way I would guess to test that, if you can can isolate the suction piping is to:
    - hook up an air compressor up to a drain plug fitting on your pump basket
    - set air compressor pressure regulator to 15 psi
    - isolate skimmer "A" using hayward valve
    - blow air through piping (should blow water out of skimmer A)
    - then plug skimmer A hole to see if any air is directed to the main drain
    - if you see bubbles at main drain, they are piped together (somewhere)
    - if no bubbles, then switch hayward valve to other skimmer and repeat procedure

    Others can elaborate if there are any risks in this plan.
    16' x 32' (21100 gal), vinyl, 1.5 hp Hayward SuperPump,
    Tagelus TA60/60D Sand Filter, Raypak 399K Digital Heater, TF-100

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    Richard320's Avatar
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    Re: Help Making Sense of Bottom Return/Main Drain

    Can you clarify this: "When the pump is running, it does return water, along with a single wall return in the shallow end."

    Water comes out the grate at the bottom of the pool?
    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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    njboater74's Avatar
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    Re: Help Making Sense of Bottom Return/Main Drain

    Again, thanks everyone for the replies. Talking this out has been very helpful. I work in technology, and often recall seemingly obvious and useful information only after I've finally asked around for help.

    Case in point, I replaced the pipes between the skimmers and the pump last year. It was a DIY job...when I bought the house one of the pipes was crushed.

    So there's definitely nothing connecting the skimmers to the grate at the bottom of the pool.

    Is there any other way that the grate at the bottom could be a drain? Or can we conclude it's just a return at this point?

    - - - Updated - - -

    Quote Originally Posted by Richard320 View Post
    Can you clarify this: "When the pump is running, it does return water, along with a single wall return in the shallow end."

    Water comes out the grate at the bottom of the pool?
    Yes, water comes out of the grate at the bottom.
    33k gallon, 40x20 IG Vinyl, Hayward sand filter, Hayward pump
    Hayward multiport valve, TF-100 Test Kit.

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    Mod Squad jblizzle's Avatar
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    Re: Help Making Sense of Bottom Return/Main Drain

    Well, sounds like for some reason the floor is plumbed as a return ... it cannot be both unless you had a valve to switch it from a suction to a return line.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

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    Richard320's Avatar
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    Re: Help Making Sense of Bottom Return/Main Drain

    Quote Originally Posted by njboater74 View Post
    Again, thanks everyone for the replies. Talking this out has been very helpful. I work in technology, and often recall seemingly obvious and useful information only after I've finally asked around for help.

    Case in point, I replaced the pipes between the skimmers and the pump last year. It was a DIY job...when I bought the house one of the pipes was crushed.

    So there's definitely nothing connecting the skimmers to the grate at the bottom of the pool.

    Is there any other way that the grate at the bottom could be a drain? Or can we conclude it's just a return at this point?

    - - - Updated - - -



    Yes, water comes out of the grate at the bottom.
    Then it's not a drain. It's a return. It was fashionable some tears ago to send the return through the drain when running the heater since hot water naturally rises.

    You won't be able to use the drain for suction unless to dig up and cut pipes and replumb things that way.

    I don't see any disadvantage to the way it is now. Many people have no main drain, and those of is that do quickly discover they don't work very well to draw away debris. ABout all they're good for s to move some water down deep to prevent temperature stratification, and your setup does that.
    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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