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Thread: Blowing Out Main Drain

  1. #1
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    Default Blowing Out Main Drain

    I closed my pool for the first time this year, using a 6 gal air compressor. I have a variable speed Pentair pump, not one of those that you can manually set to backwash, etc. I'm really confident I blew out the skimmer, returns and deck jets fine, as I got plenty of air flow, etc.

    However, with the main drain, I got some bubble but not at the level of the returns. I convinced myself that was fine, since the lines are below the frost line. Then, after taking apart the filter system, I decided to try to use my shop vac to blow the main drain for piece of mind. But no air came out. So now I'm thinking not only is there water, but by opening the valve, I probably brought even more in.

    Up all night thinking I should put the darn filter system back together again, just to make sure. The way my pvc are setup, I don't think I can put antifreeze near the filter lines for added piece of mind.

    Thoughts on putting it all back together again for the compressor, or should I try the shop vac again? BTW, my filter is not close to the pool, so the lines are pretty long, so more water to push.

    Thanks for your thoughts!

  2. #2
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    Default Re: Blowing Out Main Drain

    Bad news: you cannot reliably blow out 1.5" or 2" pool lines with a compressor; you need a BIG shop vac. The issue is not pressure, but air flow volume, needed to blow out water that may be trapped in low spots in the pipes. (I know, there should not BE low spots: but most pool guys are poor plumbers . . . and most pool buyers will not pay more to 'do it right' underground!)

    Best bet? Hire whoever has closed your pool successfully in the past, to do it again. And WATCH how they do it. Next year, do the same.

    I would offer more advice, but I'm in Georgia, and am not confident I know what's needed for successful winterization in CT. I was 8 years old -- more than 50 years ago -- the last time it got below zero here!

    Good luck!

  3. #3
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    Default Re: Blowing Out Main Drain

    Thanks. What do you mean by a big shop vac? Mine is a 5HP and the largest I've seen are 6.5HP. Is there something larger? I've seen people post that you cannot use a Shop Vac and I've watching instructional video that use a compressor to blow out all the lines.

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    Default Re: Blowing Out Main Drain

    Sorry, I can't really help. Vacuum cleaner horsepower rating are even MORE bogus than pool pump horsepower valves. "Big" means "big enough to do the job", and unfortunately, horsepower numbers supplied by the marketing departments of the vac companies are just misleading. What I always used was a Mighty-Vac, but apparently they are no longer made: https://www.amazon.com/dp/b003wlcj9o

    This may be the current replacement: Air Supply Florida Cyclone Vacuum and Blower (@ Amazon)

    I've already given you the best advice I've got, and I'm not going offer uninformed speculation on something as critical as properly winterizing a pool in Connecticut.

    Sorry.
    Last edited by PoolDoc; 10-26-2018 at 02:27 PM.

  5. #5
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    Default Re: Blowing Out Main Drain

    Bought the blower and it worked amazing. Guess we’ll see in the spring, but I’m fully confident the lines and main drain were cleared. Thanks for your help.

    Also, local hardware owner also said the air compressor doesn’t provide the volume necessary.

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    Default Re: Blowing Out Main Drain

    Glad it worked well for you.

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