Runs well after starting, but hard to start

[Shakushinnen]

Hi,
I have an inground pool (an old pool), with a Hayward pump and filter system. The system runs well, after starting, but is hard to start after being off overnight. At such time I have to prime the pump by filling the prepump basket with water, which I've never had to do in previous years. If I turn the pump off after it's running, it starts well. I have over ten years of experience running the pool, so am familar with it basic operation.
Thanks,
..... john

[Pappy]

Somehow, air is slowly getting into your pump when it is off. If there are there any tiny air bubbles in the return water, that's a good indication that you have a leak between the skimmer and pump. If you have a water leak between the pump and return, that will let air in when the pump is off. A good place to start checking for leaks is the pump seal. Do you have a check valve in the system?