I bought a house in Madison, Wisconsin this summer and I am closing my pool for the first time. It's a pretty simple set-up. 22k gallon in-ground with one skimmer, main drain, and three returns. The skimmer and drain feed into a Hayward SP-735 4-way ball valve before the pump. The pad is just above the water level.
I lowered the water 8" below the skimmer and it's just below the returns. I noticed something strange while draining. When the water got below the skimmer opening, I switched my valve to full drain, but I could hear a gargling in the skimmer like the pump was still pulling form that pipe. To stop this I plugged the skimmer until the water was below the returns.
Next I began blowing out the lines. I hooked the blower up to the skimmer and blew through the backwash line, filter, and returns. I capped the returns one at a time and poured a gallon of anti-freeze down their line from the pad. While blowing, I could hear a little bit of air coming out of the top of the 4-way valve.
The final task is to blow out the main drain and do an air lock with the valve, but I don't trust it. I tried it once already, and after the valve is closed, I can hear air getting pushed out of the top of that **** valve. The valve is cheap, and I'm thinking I will just replace it with a better one. It's strange though, that it never leaked water all summer.
What would be a good, reliable replacement valve? Where should I order it from? Should I install a redundant shut-off valve on the main drain line to further protect the air lock?