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Thread: Main drain closing question - did I do enough?

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    n240sxguy's Avatar
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    Main drain closing question - did I do enough?

    I closed my pool about a week ago. I blew all the lines, and plugged them. I blew the skimmers, put a plug in one, and a gizmo in the other because I couldn't get a plug to work. I dropped the water level to just below the skimmers, vacuumed the water out of the skimmers, and put a jug in the one with the plug, and pool noodle pieces in both. I covered the skimmer lids with a piece of old liner to keep the rain from filling them up after i put antifreeze in each. When I tried to blow the main drain, it never bubbled. I shut the valve on the main drain, turned off the blower, then opened the valve back, and could hear air coming back out from the water pushing back into the main drain. I poured two gallons of antifreeze into the main drain and turned the blower back on. I never saw pink coming out of the main drain. I closed the valve and figured the amount of air I pushed back down the main drain, plus the two gallons of antifreeze would be plenty to keep it from freezing. Anyone agree or object to this? I would've used my compressor to blow the main drain, but its 240v, and I would either need to make a 150ft extension cord, rig up something at the pool pad, get another 100ft of air hose, or drag it all the way to the pool and use what air was in the tank to blow the line. None of which would be an easy task. What say ye?
    30K gallon IG vinyl. 1.5HP 2-speed Waterway Mustang pump. 600 lb sand filter. Polaris 280. Circupool SI-60+. TF-100

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    Re: Main drain closing question - did I do enough?

    Exactly what most would do. The water in that main line can freeze, but it now can grow up the line and cause no damage. Companies in my area do not blow out main drains at all. The ball valve will leak as you saw. I go one step further, I use a cyclone and blow the main completely free of water, close valve, then add a pressure plug. This guarantees the air will keep the water from coming back up the line again.

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    n240sxguy's Avatar
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    Re: Main drain closing question - did I do enough?

    The air didn't come back out until I opened the ball valve. No way to know if the valve actually seals good or if it would have a slow leak over time and allow the water back in that line. I didn't do the math, but on a 2" line, i didn't figure it would hold more than 8 to 10 gallons of water. I displaced 2 with antifreeze and maybe another 2 with air. I could talk to the previous owner and see if he even blew that line when he closed it.


    30K gallon IG vinyl. 1.5HP 2-speed Waterway Mustang pump. 600 lb sand filter. Polaris 280. Circupool SI-60+. TF-100

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    Re: Main drain closing question - did I do enough?

    If you put some soapy water on the valve when it's closed, you can see tiny air bubbles. At least that has been my experience. Simple pressure plug ensures that air stays put.

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    n240sxguy's Avatar
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    Re: Main drain closing question - did I do enough?

    The plug would be hard to do on my setup. The main drain has a double union ball valve then t's into the manifold that goes to the pump. No good place to plug it.


    30K gallon IG vinyl. 1.5HP 2-speed Waterway Mustang pump. 600 lb sand filter. Polaris 280. Circupool SI-60+. TF-100

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    Re: Main drain closing question - did I do enough?

    If you are able to unscrew the ball valve, then a 1.5" pressure plug has enough space to bite on the ball side.

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    n240sxguy's Avatar
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    Re: Main drain closing question - did I do enough?

    I didn't realize there was that much room there. Didn't think it looked like it at the time. I'll save that trick for next year and maybe get a portable air tank to blow it out with. With pressure and gravity on my side I should be able to get out 90+% of the water then hold that air lock with the valve and plug.


    30K gallon IG vinyl. 1.5HP 2-speed Waterway Mustang pump. 600 lb sand filter. Polaris 280. Circupool SI-60+. TF-100

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