Can't blow air into main drain line for closing

[chuck1971]

I am closing my new pool by myself this year after the builder helped me last year. We just blew air into the main drain line (pressurized), and then shut of the valve to trap the air in there. I bought a 6.5HP craftsman shop vac, but can't get enough pressure in there (assumuming it is because it is trying to blow into 8 feet of water), to blow air out. I am in ohio, thoughts? I hate to pay someone to come out to pressurize the one line every year! I have a small compressor also, but to pressurize more, I would need to rig up some sort of adaptor to screw onto the line, as just trying to hold it on there and make a seal isn't getting the job done with the vac or or the compressor.

Thanks, Chuck

 

[pooladdict]

Unless you get some major pressure built up, you can never fully remove all the water from the main line. I blow my line for about 2 minutes with Vacuum, turn ball valve closed, then open it, pour in Anti Freeze, then another minutes with the vacuum, then close it while vacuum is going. As I understand, as long as any ice formation has a way to grow, you will never get problems.
I have done this for past 2 seasons, and I live in severe winters. My whole pool froze totally last year. And no worries about broken lines underground.

Hope this helps.

 

[waste]

Chuck, here's my take on it.

With a main drain, all you're trying to do is get the water in the line to stay below the frostline. If you can pressurize the line enough to do this and plug it quickly enough to stay there, you'll have no trouble 8)

To be sure that the shop vac is pushing water out, you can lay a string on the drain grate and see if it moves when the air is applied, when it stops moving, you've blown all the water out of the line that you can. (TIP - you can tie the string to your brush and place it over the drain )

 

[Durk]

I go the compressor route and air BOILS out the main drain (about eight feet under lowered water level). My compressor is in the basement and I throttle it down to 25lb (14lb will do 33ft of depth so that is plenty.) I matched an air nipple plus a bushing to a garden hose nipple/NPT adapter and run garden hose (about 120') to a hose bibb installed between the filter pump and the multi-port. I don't have that much air hose but garden hose handles 25lb of air with no problem. The hose bibb needs a double female piece of garden hose or a clothes washer hose to connect. Set multi-port to Recirc to let air through but not out to Waste.Then set your line valves on your filter system so only the line you are blowing is open and then open up the hose bibb and watch that air bubble out of your drain--then close the line valve and then the hose bibb. Throttle down to 2 or 3 pounds to plug the returns or you will blow the plugs right back out! I am in NJ and we have not used anti-freeze in 60 years of pool operation. I sure would in Canada, though.

 

[scottweedboy5]

hey guys ive been workin for a pool company for many years now one of the jobs i do is closings. i live in barrie ont it gets cold here in the winters. just gonna let ya know there is no real way to winterize the main drain in ur swimming pool due to the amount of water you would need to blow out of the line it is impossible and even if u do manage to blow it out the line is still open at the bottom of the pool it will just fill back up again. the main drain in a swimming pool will either go to your equipment if it goes there just open the valve before your pump when the water freezes in the line having the valve open will allow the ice to move up in the pipe and it should not break it. if your main drain goes to your skimmer there will be two holes in the bottom of the skimmer the one closer to the pool is usually the main drain. go to any pool store and get yourself some foam rope and stick about a 1 foot peice in the main drain hole then put your winter plug in. the foam rope crush under the expantion of the ice and the plumbing line shouldnt break. ive been doing this for almost 5 years and ive closed hundreds of pools and i very rarely very very rarely have a problem with the main drain line breaking.
If any one has any pool related question ill be more then willing to try my best to help you out

 

[JasonLion]

just gonna let ya know there is no real way to winterize the main drain in ur swimming pool due to the amount of water you would need to blow out of the line it is impossible and even if u do manage to blow it out the line is still open at the bottom of the pool it will just fill back up again.

when the water freezes in the line having the valve open will allow the ice to move up in the pipe and it should not break it.

It is possible to blow out a main drain and have it not fill back up with water. It requires an air compressor, air tight valves/plugs (not all of them are), and doing things in the right order. If the pipe is sealed at the top, the air will not travel down and so can't leave the pipe. Water can't fill a pipe that is full of air. The air will compress as it cools, so some water will get in the bottom of the pipe, but there is normally still enough air to keep the water below the frost line.

What happens when the water freezes depends on how the pipe runs above the frost line. Straight pipe runs free of any fittings from the frost line up to the water line are generally safe, but fittings (elbows, valves, etc) can often be broken by freezing even if water can flow freely. Ice will not make sharp bends and can easily break an elbow fitting.

 

[waste]

Scott, welcome to TFP!! Glad you're here 8)


I prefer (obviously) the method I gave above, but am willing to concede that the foam rope could also do the job I think it's something that plagues the industry - we keep doing what we've always done, thinking that "it's worked most of the time so far, so we will fight to the death anyone who says it might cause a problem" (esp. cya over 100) {on a personal note - I recently was told that the 'lead man' on our crew said that my 'opinion' of degreasing the filters we acid wash before they go into the acid dip was 'BS' -- "he reads too much, we've never had a problem" :grrrr: }

I also want to mention that I read an article a few years ago about the fallacy behind leaving both ends of a water filled line open to prevent pipe bursting (as I recall the study was done in Alaska - while most of the time it's fine, under certain conditions, the ice will create a plug and in between the plugs water can thaw and then refreeze which can burst the pipe)

I'm going to get the Mods attention for you (not that you've done anything wrong ) - just to get you the "In the industry" tag you deserve - it lets folks know that you know what you're saying and also acknowledges your experience :-D

Again, welcome here & thanks for sharing your knowledge!!!

Ted (A/K/A/ waste)


I see Jason has answered whilst I typed - Jason, can you change his rank?

 

[spishex]

just gonna let ya know there is no real way to winterize the main drain in ur swimming pool due to the amount of water you would need to blow out of the line it is impossible and even if u do manage to blow it out the line is still open at the bottom of the pool it will just fill back up again.

Just because it is open on the bottom doesn't mean you can't hold air in the line. As Jason stated, closing the valve with a column of air inside should hold it in place assuming the valve works. Like putting your finger on top of a straw and then putting it in water. If your valve is suspect, or in the case of the straw if you have crusty calloused fingers, that air column may leak over time.

the main drain in a swimming pool will either go to your equipment if it goes there just open the valve before your pump when the water freezes in the line having the valve open will allow the ice to move up in the pipe and it should not break it.

If this theory were true there'd be no need to prevent ice expansion in skimmers, would there? The problem is that water freezes from the top down, potentially sealing it in place and making horizontal expansion more likely.

Welcome to the forum!