Having inground installed, pool closing questions

[Jeffsp]

Hello, new member and having an inground installed. Had an above ground for a few years and making the swap to an inground pool, 14ftx22ft Grecian 3.5ft deep to 5ft in the deep end vinyl liner pool
I've read a few articles about closing, including the pool school article.
My questions pertain to blowing out the plumbing and/or adding antifreeze

I have a compressor and a shop vac, will probably start with the shop vac to see if it is sufficient enough to clear the main drain.
When blowing out returns and drains where am I hooking up the vacuum? The skimmer intake port?
After plugging the returns, the main drain then gets blown out, but ive found that the main drain doesnt need to be plugged. What keeps water from back flowing? Is it by trapping air by closing the valve?
If this Is the case, has any one ever had a problem with the valve leaking air and allowing water to flow back into the plumbing?

After blowing out the plumbing I might add antifreeze just as cheap insurance, but where do you add the antifreeze to the plumbing, and if your trapping air, then how would you add antifreeze to the main drain line?

Final question, hopefully the pool will be filled and backfilled by the second or 3rd week of August, then waiting for another month for settling before the concrete deck gets poured and then another month for curing before the concrete can be drilled for the cover anchors, so i may not have a cover till November. Is there any reason i couldnt use a large tarp with water tubes as a temporary cover?
Thank you all, I did some searching but didn't quite find the answers to these questions.
Thank you all

 

[AftonJeeper]

Shopvac set to blow air in the skimmer should clear all the return jets and skimmer. Those get plugged. I'm not sure how they winterized my main drain, I think anti freeze poured from the pump back down the main drain line.

I've seen people use tarps. Throw a few rafts/floats in the pool and the patio furniture around the edge to hold it in place.

 

[jmhjgh]

on mine there is no good way to add antifreeze for the drain. I blow everything from the far skimmer and do the skimmers and returns. Then blow main drain until I have a fountain of air coming up and then have to trust the air lock on the valve. I do not think a shop vac will do the main drain. I built a pvc fixture and quick disconnect for the air compressor.

 

[jmhjgh]

Regarding a cover. I wrap the pool in 2x6 lumber sitting on the deck and screw a tarp to the wood. I have reused the lumber each year.

 

[Jeffsp]

jmhjgh, I like that idea, should help keep the cover in place, I should hopefully have the safety cover done before the new year, but will need to cover with something once mid-late fall hits.

I do have a compressor as well, so if the shop vac can't do it, ill make a fitting for the air compressor.

Has anyone plugged main drains for winterization?
Being that my deep end is only going to be 5ft, im considering that as a possibility just to be safe.
And finally, the frost line around here is 18" below ground i believe, am I correct thinking that water down at the drain shouldnt freeze?
Thank you all again.

 

[jmhjgh]

The issue is if the air lock fails, the water in the drain line will be whatever the water height is in the pool. We have a 42" frost line in Minnesota. I never feel very good after winterizing.

 

[Jeffsp]

Correct, that is my fear. For now, I'm planning to probably blow the pipes out and then plug them, including the main drains, and then open the system at the pump and send some antifreeze down.

One thought I did have was that with everything else plugged, even ifbthe valve leaked air, evrything else in the system is plugged and should also act as an airlock, can anyone confirm that is correct?

 

[jmhjgh]

That is correct. Do you have a deep end? If so, staying down without scuba equipment is very difficult.

 

[Jeffsp]

Deep end is 5 ft deep, so once pool level lowered about 3.5-4ft deep. I'm figuring it would be a little bit of a hassle, but i believe it the drain covers are only held on with 2 screws, so one screw per breath and then the plug.