I am going to 2 inch and wanting to Replumbing it because when installed they used ball valves which after 3 years are already getting difficult to turn. I have heard some put 2 way valves from the intake to the solar pool heater and going back to the pool but not sure I need because of check valves on return line and I was looking into 3 way drain down valves but have heard so many issues with them leaking etc and was wondering if I left the one cracked just a little it would be ok to allow drain down at night when pump isn’t on or drilling a small hole to allow drainage which I have read a couple people have done just don’t want water going back up when I close the solar pool heater down for the winter. Am I missing any valves or do I need to change anything before proceeding? Any help or suggestions etc are very welcome. Appreciate all the help