New Pump/filter, new leak

Greetings, could really use some help. Just bought a house last year with a 35 year old Sylvan inground pool, with original filter, newer pump motor. I decided to upgrade both, going to a Hayward sand filter and Hayward 1.5 hp filter. Both seems to work very well, the pump is much more powerful than the one it replaced. But one thing, the pool leaks an inch of water a day, but only when the filter system is running. I did not notice any leakage before on the old system. There are no evident leaks in and around the pump/filter. It is possible that the pump is too strong and may have created new leaks in the suction lines are return lines?

Thanks

Don't know if it created new leaks, as much as it could have exposed an existing leak with the increased flow. Due to the other pumps low flow, there may have not been enough flow to make the plumbing leak before.

Welcome to the forum. Would help to know the surface area and capacity of the pool in gallons. Rough estimates are fine. Reason for asking about the surface area is to get a better handle on the size of the leak. i.e. what does an inch of water mean in gallons. The conversion is about 7.5 gallons per cubic foot. If it is a pipe or joint leaking it would definitely be on the pressure side. If the plumbing is original you could very well have a crack somewhere due to ground settling and stressing a joint or pipe itself. Or, freeze damage? I'm thinking one weak spot would be around the return penetrations into the pool. One way to prove a leak in the return plumbing would be a pressure test using compressed air. If you feel comfortable messing with things then it really isn't that hard to do. If you want I can give you more details. You would have to blow the water out of the pipes as you would do for winterizing and you would need an air compressor of some sort. Even one of those small 12 volt things will work.
This is a start.
Al