Hi! We have had our inground pool for 8 years now and I've always closed it myself by the same method; using a shopvac as a blower to clear the lines.
This year something is different. I can not get ALL of the returns to blow out properly. We have one line from the heater that splits underground to return water to 3 eyeballs on the pool walls and 2 eyeballs on the steps. Drained the pool to the point where the eyeballs on the steps are just, but completely, above water. The other 3 are submerged. No different than past years.
I usually plug all five returns, have a helper apply air pressure to the main return line while I go around and open one return at a time, blow the water out, replace the plug and go on to the next. I usually repeat the cycle until I'm confident that all the lines are clear.
This year I was able to get air to come out of each one, but not all in each cycle! There was always one that wouldn't clear, but not always the same one. When I would remove the plug expecting air to come out, instead I can feel the water being sucked back in! But if I go to a different one, air rushes out.
Very frustrating! I don't understand why it could be doing this. (BTW, clearing the skimmer lines was no problem.)
Can anyone help?