I am closing my pool and have blown out and plugged all of the skimmer and return lines. However I am very confused about my system when attempting to blow out my main drain.
There are two pipes going into the pump. One of them has a jandy valve, I assumed this is the main drain pipe. However when the valve is open and I am pumping air into the system air does not escape from the main drain. In fact the pressure builds and eventually one of the return lines give in and plug blows. When I close the valve however the main drain does get blown out. Which is very puzzling to me. How would I seal the main drain?
Please let me know if you need me to provide any more info.
Thanks in advance