A thought on blowing out the drain line

anthonypool89

Well-known member
Aug 26, 2016
216
Berks County, PA
Here's something I always wondered about - I have the old anthony pool set-up which calls for a double plug (#8 and 9) in the skimmer (lower one plugs the line to the drain and the upper plugs the 't' joint where the skimmer line goes off to the pump).

So, once I'm done blowing out the drain and plug it, theoretically when I open in spring and pull that plug there still SHOULD be pressure behind that plug - but there never is. If I feel I need to redo the blow-out while closing, there is always aLOT of air pressure in the drain line that bubbles back up into the pot when the plug is pulled. So I can only assume that with the skimmer filling up repeatedly during the off-season from rain and snow/ice melt, eventually I suppose at least part of the drain line is compromised.

I've never been that concerned about it since I always add 2 gallons of antifreeze after blowing the lines as a precaution - one gallon goes into the returns and the other into the pump / skimmer line. And, until things freeze up, I do my best to always keep the water level below the skimmer and then suck all the water out of the pot. If no water fills back in from below, I assume the drain line is still reasonably plugged. I always think back to something my Dad always said when he used to help me close the pool, which is that if the water in the drain line would freeze all the way (or even a good part of the way) down to the drain, it'd be "one heck of a winter"! Probably true.
 

Catanzaro

Platinum Supporter
TFP Guide
Jul 30, 2014
3,403
Monmouth County, New Jersey
It is possibly that air, when it warms up kind of expands, and the opposite when it cools down. The air may still be trapped in there, but temperatures is probably what affects everything. Think about your car tires when temperatures suddenly drop or in the summer how much more air your tires have in pressure. I believe it is the same type of concept, but could be wrong.
 

Newdude

Well-known member
Jun 16, 2019
1,512
NY
My lines all have a vacuum after the winter. I by dumb luck opened the screw in plugs first the first few years. One year i did the rubber stopper at the equiptment pad first and it sucked it in past a 90 degree bend faster than i could react. 30 minutes with a shopvac and a whole lotta prayers and curses later i sucked it out. Lesson learned to always open the gizmos / return plugs first.
 

Yinn

Member
Apr 12, 2019
21
New Jersey
My lines all have a vacuum after the winter. I by dumb luck opened the screw in plugs first the first few years. One year i did the rubber stopper at the equiptment pad first and it sucked it in past a 90 degree bend faster than i could react. 30 minutes with a shopvac and a whole lotta prayers and curses later i sucked it out. Lesson learned to always open the gizmos / return plugs first.
Yea nobody tells you that about those plugs. Mine is still in there somewhere....
 
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