new user/new pool owner

I just bought a house with a pool but am allowing the previous owner to rent from me for a few months. The pool is currently closed from winter and still covered. After closing (against what he said prior to closing) the previous owner said he wasn't going to open the pool this year...I assume to avoid the cost of opening it and maintaining it. Will not opening the pool cause a future problem with it being VERY hot in the area we live in...the south. I own the home so I can open the pool if I choose and force the renter (based on rental agreement) to maintain it.