How are you making your joints?

Are you using teflon tape on all the threaded joints? Or Teflon paste? These are a must.

Are you using glued joints elsewhere, and are you using Schedule 40 fittings and flexible PVC glue? If you are using flexible PVC pipe (called TigerFlex) and are using internal fittings with it you will need to replace them all with glue-on Sched 40s or it will NEVER stop leaking.

If you are using internal, barbed fittings (on other types of flexible) are you using teflon paste first?

The BIGGEST problem with leaks and pool plumbing is people use TigerFlex with internal fittings. Professionals do it to. The installers were driving away and the fittings on the pump were leaking for me! I replaced all the internal fittings with glue-ons and was done!

I had installed solar panels for my parents about 4-5 years ago and used T/F with internal fittings on the pool store guy's say-so. Leaked even with 3 hose clamps per fitting. Replaced it with glue-ons--problem solved.

But I have no expertise with roof-mounted solar panels and the pumping requirements for that. Others will have to help you.