A Y might help there, however all Y's that I have seen are DWV drain pipefittings, not schedule 40 pressurized PVC pipe, and while roof top solar is a relatively low pressure application, it is also at well about the generally suggested operating temperature for PVC, so I would have some concerns about using a DWV fitting that has a much shorter socket depth and may be thinner than standard schedule 40 at that location.
Ike
Ike