Hello! First post here. Brand new pool owner and thankful for finding Trouble Free Pool! Now that I am nearing the end of the swimming season and considering what it's going to take to close my above-ground pool, I'm confused about how to handle the main drain. Part of the confusion is that much information / postings about main drains has to do with in-ground pools.

Here's my setup: 24' diameter 52" deep, above ground, vinyl-liner pool with 2 main drains +/- 5' apart in the center of the pool. The main drain line is flexible PVC (guessing 2") and comes out of the ground at the edge of my pool to a control valve in front of the pump filter basket.

I live in the mountains of west-central PA (+/- 1 hour East of Pittsburgh) and winters are quite cold with snow on the ground generally from Dec through April. Temps close to 0 F would be common.

Question: How should I winterize the main drain line? Should I "air-lock" it? - I don't really see how this works since the water at the bottom of the line would still be above the frost line level. Should I add anti-freeze? (I'm confused on how to add it with water filling most of the line.) Or should I do no more than tie it up vertically above the top of the pool rail and leave the end open for ice expansion? (Found this link for support of the latter: http://www.edwardspools.com/blog/bid/40189/Main-Drains-In-Above-Ground-Pools-How-Do-You-Winterize-Them)

Thanks!
Garry

Does the pool freeze solid?

I have no idea if the pool will freeze solid. This will be our first winter with the pool and I don't know anyone else in the area with a pool. Seems to me it would either freeze solid or come darn close.

Garry

If the pool freezes solid then the ground under the pool could freeze too which means you need to add antifreeze to the line to ensure it doesn't freeze solid. Just pour it into the plumbing until you see it start coming out in the pool then valve it off.

That's it? The antifreeze will stay in the line? How much antifreeze should I expect to need? I'm guessing we're talking about 18 feet of 2" line. I might have to buy a separate valve to shut off at the end due to the way it will disconnect from the main 4-way valve.

The pool store had told me when we bought the pool that they would likely have to close it since it would involve a super-duty shop vac and most home owners just don't have powerful enough equipment. What method might they be talking? Air-locking? Is this any better than antifreeze? I was looking online and came up with a super cool idea to make a homemade PVC end cap with a schrader valve similar to this:


Any thoughts on air-locking vs. antifreeze?

I do have a small air compressor (125 PSI max) and a medium duty shop vac to work with.

Thanks,
Garry

If you knew that some part of the MD line was below the frost line, air locking it would be better, but if it's not below the frost line then any water in the line is going to freeze. If you can install a plug in the MD inside the pool while you're blowing it you may be fine to blow it.

Another thing you could do is attach a hose or piece of pipe in the MD long enough to extend above the waterline and blow the water out of it. A high volume, low pressure, air source is what you really need to blow it out. An air compressor won't normally blow all the air out but what you could do is blow it with the air compressor and then with the shop vac or leaf blower.

Ok, so it sounds like it's easiest to stick with the antifreeze. Am I understanding correctly that RV Antifreeze is fine to use? (I understand not to use automotive engine antifreeze.) How much might I expect to use? The antifreeze will just stay in the line the whole winter, and not seep out of the MD line into the pool? Will the end of the line have to be capped off? What if I leave it open?

Thanks,
Garry

You'll need about 3 to 4 gallons. It'll stay in the line fine. I wouldn't worry about capping it off.

Ok, stopped by my local pool store today and talked with them about how they winterize the main drain. This guy seemed very knowledgeable and has been closing pools for 20+ years. He told me to disconnect the 3 way valve from the filter basket (cap with plug), & remove hose from skimmer. Use 5+ hp shop vac to blow water out of main drain from the skimmer end of the skimmer hose and then quickly shut valve (air lock it). Fill skimmer hose with antifreeze (use about 1 gallon). Quickly open valve and run shop vac to blow antifreeze down into MD line & stop before blowing it completely through into the pool (only about 5 seconds). Then quickly close valve, remove skimmer hose and use expansion plugs to plug other 2 ends of the 3way valve.

Questions - First, If you could simply just pour antifreeze down the line (no blowing force of any kind), why wouldn't they be doing this? Second, only 1 gallon of antifreeze? Doesn't sound like enough, however I believe he told me the bottom end of the line (under pool) isn't what needs protected (because it won't freeze), but that you just want the antifreeze in the exposed end of the line. Third, I don't like the idea of capping the line off completely because it doesn't give anywhere for ice expansion to go in case something didn't go right. (Okay, #3 really wasn't a question.)

Any thoughts? I'm thinking to just try this "pour it right in" method myself first. They are $65/hr to close and should only need an hour or even less to do it. I could call them if I run into a disaster.

Garry

Your plan sounds good.
RV antifreeze is slightly heavier than water so you can pour it through water but most professional closers can't take the time to do that so they blow the antifreeze into the lines. It makes it faster for them.

P.S. If the antifreeze is where you can see it, don't be alarmed if you see it freeze. It will freeze. The difference in it and water is that the antifreeze shrinks when it freezes and water expands.

Thanks Dave! I did wonder if the "pool guys" did it their way due to not having the time to wait.

Garry

Just a follow up for anyone searching for this information. I closed the pool this weekend and all went very well. Adding the antifreeze down the main drain line was so simple anyone could do it! I disconnected the main drain line along with the 3-way valve from the filter basket, swung it straight up in the air (it's flex PVC) and tied it against a post. This put the open end of the main drain line about 12 inches above my pool top rail and my water level was already drained about an inch below the skimmer. I then just started pouring RV antifreeze down the main drain line. I had expected the line to fill up quickly, stop and wait for it to drain down, add some more, stop and wait, etc . . . but it never rose to the top of the pipe even when pouring full force. At 2 gallons of antifreeze I started seeing pink rise through the main drains in the pool (both). I went ahead and added a 3rd to be sure I had enough. All in all this process only took about 5 minutes!

All I can do is laugh at the procedure the pool store guy told me! It would be ridiculous to go through all that hassle when all you have to do is pour it in! Only thing I can think of is that the pool store's shop vac method would be necessary if you didn't have enough main drain line to rise it above the water level - OR - you had a main drain line plumbed with standard PVC and not the flexible type.

Grateful for all the assistance from this forum! (Thanks Dave!)

Garry

I have a 24' with a center drain as well. this is my 16th season. I plug the center drain with drain plug . Next lower free end to ground to drain as much water as drains easily . Then raise end and hang from pool ledge with string or bungee cord (i have used both ) Next poor antifreeze into drain line to top and plug . use maybe 1/3 gallon antifreeze . Much easier/quicker/cheaper than any above discussed methods.