Blowing out New Main Drain in AGP.

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brianosaur

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Jun 16, 2014
3
Long Island, New York
Yeah, sorry for another main drain thread. Closing time is approaching here in NY and I am planning ahead.

I changed the expandable liner in my 24' rnd x 60"d AG pool (semi-IG) at the start of the season this year.
After the old liner was out and before the new liner was in I installed a Hayward Main Drain in the center.

I then ran a 2" pvc pipe from the side fitting of the main drain sump, under the pool wall and up and out of the ground. From there the pipe ran to a ball valve, a 1 1/12" reducer & pipe, and to a removable threaded union.
The 1 1/2" pipe then ran to a Y-fittlng with the skimmer and then over to the pump.

I plan on using my air compressor to blow out the MD line.
Whats the best way to go about this?

I read you can air slam the ball valve and water wont back up into the pipe. However, the pipe leading from the sump doesn't run vertically out of the bottom. It is horizontal with a pitch down toward the MD as the center of the pool is 12" deeper then the side walls. Wont SOME water back into the pipe?

I see they have rubber plugs with a wing nut and a blow thru valve in the drain.
winter_plug2.jpg

Is the type of valve on this plug a standard bike tube Schrader valve?
So that it blows air FROM the wing nut side TO the rubber plug side?

Is it just a threaded hollow tube and air can pass both ways?

Or is it a valve the will let air blown from the rubber plug side out toward the wing nut side?

Should I swim down and put a plug in the MD itself? Can I use the one shown or do they have a 2" one way blow out valve plug the wont let air back into the line once the compressor is shut off?

Thanks for any help.
 
How big is the main drain? Do you have a shut off valve if you blow air that an "air lock" can be created? Maybe posting some pictures of the piping and main drain would help me guide you through the process. Not all pools have similar plumbing, but at the end of the day all pools are basically closed the same way (air, air and move air). Thanks!
 
Is your md under the frost line? If not then any water left in the pipe from the md outside of your pool wall will be subject to freezing. Unless your pool freezes all the way to the bottom in the winter, the portion under the pool itself will be protected. The plug is necessary. It will take a substantial volume of air to push it out of the md. Trying to move that much air through a schrader valve might prove problematic.
 
Water will absorb air. So even with an "air lock" trapped in the pipe the air will be absorbed into the water and the water will creep up into the pipe. Standard problem with using an air pocket for a water slam preventer in a water line. Got to use the plug.
 
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