I thought I would post up a description of a dry run I did blowing out the lines on my pool in prep for closing next month. In the past, I've paid the pool guys to do the close, but this year I thought I would give it a shot and use the $250 elsewhere!
Now, my pool plumbing is pretty simple so it may not work for everyone, so I'll give a brief description of how it's plumbed. I have 3 returns, 1 skimmer, and one side wall suction on a vinyl pool. The plumbing is 1.5", and each line is a separate run back to the pad. The 3 returns are tied together just under the ground near the pump pad with a "3 into 1" fitting that's 2 inch by 1.5" times 3. No valves (I plan on remedying that next spring). The main suction and skimmer are plumbed on 1.5" lines back to a 3 way valve so i can put the suction between either the skimmer, main, or both. So....pretty simple set up, really.
I used a pretty cheap Craftsman pancake, 6 gallon. It pressurizes to 150 psi, and has a regulator I cranked down to 20 psi. I blew from the pump using a brass nipple screwed into one of the drains. I screwed a male compressor hose fitting like this onto the nipple.
That attached to the female end of the hose that was connected to the tank. Before I made the connections, I opened the pump strainer lid and drained most of the water, and put the multiport valve on the sand filter to RECIRCULATE. Once the air was going, I cranked the regulator up to 20 psi to add air to the lines.
The return closest the pad blew first. Once that was plugged, the next closet return blew, then the main side wall suction, then the far side deep end return, then the skimmer last. The compressor was running thr entire time, but I never lost pressure since the tank stayed around 35-40 psi, and the output was at 20. I'm not sure if a smaller capacity tank would have kept up, but as long as the input is higher than the output, it should be ok. Since I know my compressor will blow the lies with no issue, I feel confident that everything should go smoothly.
Famous last words!