Is blowing out main drain in an inground pool really necessary? Closing pool.

[jmosk335]

I am trying to figure out if blowing out the water in our main drain pipe in our inground pool is really necessary. Our pool is 10 feet deep in the deep end and water would never freeze at that depth even with our harsh winters here in Northern Ontario (Canada).

Our neighbour has had a pool for more than 30 years. It is an inground vinyl pool with a 8' deep end. He has NEVER done anything related to the main drain when winterizing/closing his pool and has never had any issues. He does clear water from the return and skimmer lines (but does not use antifreeze). He helped us close our pool last fall and so we did nothing to the main drain (didn't occur to me that there was even a way to do that) and it was fine. When we opened the pool in the spring we had a very difficult time getting water back into the pipes (including the main drain) and priming the pump. This suggests to me that there was a lot of air in the main drain pipe even without taking any action to clear it.

Also, my thought was that if the water does not freeze at that depth, and the drain at the bottom of the pool is open (which it always is), if water did start to freeze in the main drain pipes, wouldn't it push water back into the pool. In other words if some ice formed, it would not form down to a ten foot depth and therefore any pressure caused by expanding ice would just push the water that was not frozen back into the pool. If you leave the valve for the main drain (near the pump) open, that would give additional room for freezing water to go to.

There may be an obvious flaw in my logic that I am missing. Would appreciate hearing others perspectives on this.

Hi there, I was wondering the same thing, I was able to blow out my skimmers and returns, but having issues blowing out the bottom drain of the pool. I share the same logic and was wondering if you actually do this and has it had any major effects on your pool?

 

[Newdude]

The deep end side is fine. It's well below the frost line, roughly 3 ft (?) for PA.

The problem is the pad side. The water in that pipe will be at the pool level, however far you drained for closing, but still in the freeze zone. So you definitely don't need that pipe clear, but you need the water pushed down and airlocked at least to the frost line.

 

[TyTyTy]

Bump
I too have been told recently by our PB that the main drain need not be touched at all for the winter. Does anyone else not do anything to the main drain? Skimmers and returns blown out. Why is main drain different?

 

[wireform]

The main drain needs attention before winter just as the rest with one difference which is that unless you dive deep and remove the drain cover and plug it, it won't be plugged. To winterize the main drain which is piped to the pad you'd blow it out till air bubbles come out in the deep end and then close the valve to it 100% so it remains airlocked. As long as the water is pushed out of it below the freeze line you're good to go.

 

[Newdude]

As long as the water is pushed out of it below the freeze line you're good to go.

This ^^^^^^

The pipe under the pool is fine unless the pool freezes literally solid. You only care about pushing enough air into the run so that whatever water is left is below the frost line.

Most pool plumbing drops 2-3 ft right at the pad and that's enough for most of the country to not freeze. (Sorry Michagan )
If I blow back to the red circle, I'm good.

 

[TyTyTy]

This ^^^^^^

The pipe under the pool is fine unless the pool freezes literally solid. You only care about pushing enough air into the run so that whatever water is left is below the frost line.

Most pool plumbing drops 2-3 ft right at the pad and that's enough for most of the country to not freeze. (Sorry Michagan )
If I blow back to the red circle, I'm good.

View attachment 463099

Thank you. We have gotten several days now in the low 20s at night and most days in the mid to high 30s. I guess I am not sure what the best plan of action is? We have a day this week on the mid 50s. Should I try to blow it out then? Or should I just leave it be at this point? Not sure if I can make it worse if I blew into a possibly (likely) frozen pipe... Thank you.

 

[Newdude]

It was 22 last night but the ground is still 40+. There's no ice yet. I'd try to airlock it.