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Thread: Why are there two holes at the bottom of my skimmer?

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    Why are there two holes at the bottom of my skimmer?

    One of the hole is the suction line to the pump. The second hole - what's it for? Is it connected to the main drain? If so, how do I clear it or treat it for winter? This is a concrete, above ground pool in a cold region.
    Concrete (gunite) inground pool and spa (80,000 litres/21,000 gallons)
    Hayward H350 natural gas heater (electronic)
    Goldline Aquarite chlorine generator
    Hayward pumps, Hayward Pro Series sand filter, Goldline valve actuators

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    Re: Why are there two holes at the bottom of my skimmer?

    the second pipe is supposed to be for another line that is put thru the pool wall as a "equalizer" line
    so if the water drops below the skimmer on topthe other line will take in water and you won't burn up the pump.

    Few pool builders install this . I do not know why not

    james

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    JasonLion's Avatar
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    Re: Why are there two holes at the bottom of my skimmer?

    Typically the second line goes to a main drain. Often, builders only want to stock one kind of skimmer, so they stock the two line skimmer and plug the second line when there isn't a main drain or when the main drain is plumbed separately.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Re: Why are there two holes at the bottom of my skimmer?

    Welcome to TFP!!

    The second line can be used for 3 things (anyone who uses the first 2 is a moron )

    #1 A balance line (as per drjames) as was said it's a below water line that "supposedly" keeps the water in the skimmer at the same level as the pool. It's a great idea on paper but the pump is drawing more water than the atmospheric pressure can refill - hence, the skimmer doesn't refill, air is sucked into the line and the damage that this is 'supposed' to prevent happens anyway. (they are also a PITA to winterize!)

    #2 Plumb a main drain via the skimmer (as per Jason) - What a moronic idea!!! The valve in the skimmer to control the flow between the skimmer and main drain is highly susceptible to failure and if the main line from the skimmer breaks - you are SOL! Also, it's far better to have the suction lines separate - it allows more flow to feed the pump. It also has the same problem with keeping the skimmer 'fed' with water if the water level drops. It's also a PITA to winterize!

    #3 A reserve line - this is about the only option that makes any sense. When you plumb the pool you run 2 parallel lines from the skimmer to the filter pad, you only plumb one to the pump, but leave the other stubbed up (capped and plugged) to be used if the original line fails for whatever reason. The problem with this is that since the pipes are run together, what breaks 1 will probably break the other, unless it's freeze damage and the reserve line has been kept dry.

    As far as I know those are the only reason for the second port in the bottom of a skimmer, if yours is open it's not a reserve line.

    For winterizing it needs to have the water blown out of it and be plugged. If it is a balance line or a main drain line, let me know and I'll tell you a way to winterize it
    Luv& Luk
    -Ted

    Having done construction and service for 4 pool companies in 4 states starting in 1988, what I know about pools could fill a couple of books - what I don't know could fill a couple of libraries :-D

    POOL SCHOOL, TF Testkits, Jason's Pool Calculator, CYA vs. cl chart, (Just a few DARNED handy links!)

  5. Back To Top    #5

    Re: Why are there two holes at the bottom of my skimmer?

    Thanks for all the replies. It seems to be connected to the main drain. It is not plugged and the water level matches that of the pool. I was talking to my local pool supply shop and they told me to shove a few feet of foam rope into it. The foam rope is supposed to absorb the ice expansion. I don't know, this seems highly inadequate since we get some pretty hard winters here (Toronto, Canada).
    Concrete (gunite) inground pool and spa (80,000 litres/21,000 gallons)
    Hayward H350 natural gas heater (electronic)
    Goldline Aquarite chlorine generator
    Hayward pumps, Hayward Pro Series sand filter, Goldline valve actuators

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    Re: Why are there two holes at the bottom of my skimmer?

    Concrete aboveground is very interesting. Did you have it built?

    Do you have a picture of your pool? Do you know the reason for using that type construction?

    PS - add one more use for the second hole.....it can be used to connect another skimmer in "series" to save on some plumbing. The skimmer closest to the pump would have both holes open with one going to the pump and the other going to the other skimmer.......it takes a special device to balance the flow but it works fine.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    JasonLion's Avatar
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    Re: Why are there two holes at the bottom of my skimmer?

    Quote Originally Posted by waste
    #2 Plumb a main drain via the skimmer (as per Jason) -
    Oh, I completely agree, not a good idea. But it is far more common than one would hope.

    coilerman - The foam rope can work well if you are sure it reaches to below the frost line. Often enough the skimmer to main drain pipe goes straight down to well below the frost line and using foam rope is a good solution. If there are bends, you usually can't be sure how far it runs horizontally before going down again and then foam rope isn't such a great idea.

    There are only two other options. You can plug the main drain, not fun in the fall, and get lots of anti-freeze into the pipe. Or you can pressurize the pipe with compressed air, forcing all the water down below the frost line, however it can often be tricky to get a good enough seal to hold all winter.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Re: Why are there two holes at the bottom of my skimmer?

    The only advantage I see to 2 holes in skimmers is that one is 1.5" and one is 2". So if im running 2 I hook to that, if im running 1.5 I hook to that and itsaves me the risk of one less glue or silicone joint underground. I would never run a main drain off a skimmer or do an equalizing line for the reasons above.
    Matthew
    Involved in the pool and spa industry
    Pittsburgh, PA

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    Re: Why are there two holes at the bottom of my skimmer?

    Quote Originally Posted by duraleigh
    Concrete aboveground is very interesting. Did you have it built?

    Do you have a picture of your pool? Do you know the reason for using that type construction?

    PS - add one more use for the second hole.....it can be used to connect another skimmer in "series" to save on some plumbing. The skimmer closest to the pump would have both holes open with one going to the pump and the other going to the other skimmer.......it takes a special device to balance the flow but it works fine.
    Typo - it's an inground. Sorry.

    Also, I'm sure I only have one skimmer.
    Concrete (gunite) inground pool and spa (80,000 litres/21,000 gallons)
    Hayward H350 natural gas heater (electronic)
    Goldline Aquarite chlorine generator
    Hayward pumps, Hayward Pro Series sand filter, Goldline valve actuators

  10. Back To Top    #10

    Re: Why are there two holes at the bottom of my skimmer?

    The second line from the skimmer in my pool is used for a supply to bring water from the pool to my second pump which feeds the optional jets in my swim out. Like a spa area. The second skimmer has it set up to feed my water fall which will have a seperate pump that can be turned on or off from a switch on my patio
    Tom

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