I am new to pool ownership and would welcome any tips or suggestions. I recently purchased a house with an inground pool of "unknown origin". Don't know the make or when it was installed. A couple of neighbors think it may have been installed in the seventies. It looks to have been well maintained. Liner and cover are only a couple of years old. Pump was replaced last year and filter seems in good order.

18 x 36 vinyl with no steps (3' to 8')
Hayward s200 sand filter
New Hayward Super Pump Series

I'm learning all about chemistry this Spring, so any help is appriciated