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Thread: no main drain valve in my in-ground pool?

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    no main drain valve in my in-ground pool?

    Hi pool experts,

    I'm a novice and I closed the pool to day for the first time, I used a Husky 20gallon air compressor at 15-25psi connected to the pool pump drain. everything worked fine I plugged all openings, skimmers, jets etc.
    now the problem is that the air started to rise out of the main drain, but I couldn;'t find the main drain valve. I heard I am supposed to close that main drain valve in order to create an air lock.
    I don't think the pool has one (in-ground, 50x25ft, about 8ft deep, 25+ years old). I have a red valve at the suction side but whether I opened it or closed it, it didn't make any difference. The air was still blowing out the main drain.

    Can I leave it the way it is (open)? I already covered the pool and removed filters and pumps
    I think here in Baltimore, MD it wouldn't freeze that deep down anyways, what do you experts think?
    thanks a million for your advice!

    Savas

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    4JawChuck's Avatar
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    Re: no main drain valve in my in-ground pool?

    My pool doesn't have a main drain valve either, it enters the system at the skimmer with a vacuum control plate.

    My work around was to purchase a 2" expandable plug and drill a hole through it for a long pipe nipple which I threaded a "snifter" valve onto which is basically a tire air valve with an NPT end.

    Here's what one looks like, all plumbing supply places have them since there are used in pressurized water systems.



    1/8" long pipe nipple;



    1/8" pipe coupler;



    2" expandable rubber plug;



    Drill a 3/8" hole offset through the top of the rubber plug and 1/2" holes through the metal end plates for clearance, once the plug is tight in the skimmer hole and adjusted push the 1/8" pipe assembly with attached snifter valve through the 3/8" hole (with a little water for lubrication) and voila you have a skimmer plug capable of holding the small amount of air pressure needed to keep an air lock in your main drain. The press fit of the rubber on the brass nipple is plenty to hold off the few PSI of pressure in the main drain line needed to maintain an airlock.

    Ideally it would have been nice to make an adjustable plug with a larger threaded bolt which I could have drilled and internally threaded for the snifter valve but I could not find anything like that around here so I made my own. My pool store guys just looked at me funny when I asked and said they never air lock the main drain on any pools around here. Next year when I have more time I will build a proper one, the center bolt on the expanding plug only needs to be 5/8" dia to make this work.

    Might be overkill but I am not taking any chances, I still haven't figured out why they don't sell something like this...its easy to make.
    55 Kilolitre in-ground 18'X36' vinyl lined kidney shape, 1HP pump, Jacuzzi 250lb sand filter, RayPak Delta T 200K BTU natural gas heater. New PoolWerks "Blue Diffusion" liner on May 26th-2011
    Avatar is my pool!

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    Re: no main drain valve in my in-ground pool?

    thank you for your reply 4JawChuck, it's pros like you i was looking for; and it's amazing, even in canada the pool guys don't air lock the main drain?
    I have a salt water pool and hope it'll help a bit reducing the freezing temp but was told not to put my hopes up too much
    now, I don't want to sound like a conspiracy bro, but the whole thing about freezing pipes sounds a little like a marketing tactic to sell winterization services.
    Sure we should get some of the water below the frost line, add some anti-freeze, but unless you live in antartica it shouldn't be too much of a problem.
    Since, i am no expert I am curious to hear if anyone indeed had experienced damage from freezing. elsewhere i was told that pvc pipes are pretty strong; hence
    the ice would need to last for many days.

    another question about the main drain: here in Maryland the watertable is pretty high where I live (see my basement . I read the main drains have a function that allows ground water to get into the pool via the main drain. wouldn't an air lock somehow prevent that?

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    4JawChuck's Avatar
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    Re: no main drain valve in my in-ground pool?

    Well my pool is 19 years old and I doubt the main drain was ever "airlocked" so I don't doubt the PS is correct in it not being necessary even up here where we get -40C temps, the problem as I see it is they just don't plumb the pools for this feature and get away with it year after year and once its out of warranty its no longer their problem...so there is no problem! Pools here are plumbed underground with smooth wall flexible pipe since rigid stuff would crack in the first year so it pretty durable, but after 20 years any plastic gets brittle so I don't take any chances...I still don't understand why there isn't an off the shelf expandable plug with snifter valve attached...seems like a no-brainer to me.

    As for your main drain overflow for ground water I haven't seen anything like that here, they run a line to the deck that leads to a weeping tile setup under the pool so if the ground water goes higher than the pool it overflows onto the deck instead of into the pool (you could also hook up a pump to this line), I imagine its possible to plumb that line to the pool but I can't imagine why you would want that to happen...I would rather it dumped out into the yard than into my pool!
    55 Kilolitre in-ground 18'X36' vinyl lined kidney shape, 1HP pump, Jacuzzi 250lb sand filter, RayPak Delta T 200K BTU natural gas heater. New PoolWerks "Blue Diffusion" liner on May 26th-2011
    Avatar is my pool!

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    Re: no main drain valve in my in-ground pool?

    Chuck, they certainly do make expandable rubber plugs with the 'tank valve' (that's what I've always heard them referred to as) and they are VERY useful when no valve was installed on the line. (I'd check someplace like In The Swim for them, though most pool stores should be able to get you one)

    Failing to find or make one of those - with 2 people and a little practice, it's possible for one person to work the blower and the other 'slam' a plug in the pipe as soon as the blower is removed. It may take a couple of tries to seal the line in less than 3~ 2 seconds - but that should keep the water below the frostline.
    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!)

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    4JawChuck's Avatar
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    Re: no main drain valve in my in-ground pool?

    I checked the "In The Swim" website but didn't have any luck, likely a part on the shelf with a unique name so it would be hard to locate online. I checked two knowledgeable pool stores locally and they told me not to worry about it since its a non issue. I tried the vacuum blower route and there is no way I could get enough air pressure from a 2HP Shop Vac to blow that line out. So I McGyver'ed my own, cost me $10. No problem blowing the line out with my air compressor!

    I filled the skimmer and return line with antifreeze and packed the chamber with pool noodles so I am happy. I even built my own pool cover pump since the cover pumps here were about $300, I cut a 5 gallon pail and mounted a 1/4 HP sump pump in it with a backflow preventer valve and 1 1/4" line to the street, filled the drilled out pail with pool noodles to keep the pump centered and tied it off to the side of the pool with a sand filled pail for easy removal once the snow hits. I needed a spare sump pump for emergency usage anyway and paying $300+ for a tiny Rule 1800 pump just didn't make financial sense to me, not to mention the sump pump I bought is excellent quality and has an electronic sensor that shuts it down if it freezes.

    Anything pool related here costs a small fortune and the season is so short so these were my inexpensive solutions.
    55 Kilolitre in-ground 18'X36' vinyl lined kidney shape, 1HP pump, Jacuzzi 250lb sand filter, RayPak Delta T 200K BTU natural gas heater. New PoolWerks "Blue Diffusion" liner on May 26th-2011
    Avatar is my pool!

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