Lot of newbies today...welcome to the forum. Don't have an answer to your problem but I can say that leaks and that sort of stuff won't cause your problem. We have to ignore what the old system was doing and concentrate on the new system characteristics. The rise in pressure tells me the filter is plugging with something in the water. I assume the pressure rise of 10 PSI is gradual over the time you mentioned and not a sudden step. Post some additional info:
--Complete chemistry readings (FC, pH, TA, CH, and CYA) or whatever you have and how you got it.
--Type of pool (vinyl, gunite, fiberglass, etc)
--Filter and pump model numbers (so we can determine if they are matched correctly)
--Type of sanitization, chlorine of baquacil.
That's it for starters.
Al