We are often asked whether or not if it is okay for dogs to drink pool water. Our general reply is why not just provide them with a fresh bowl of water when outside. Yes, dogs eat plenty of odd things from cat feces to any scrap of rancid food on the street. But just because they do, does not me we should let them or encourage them, and the same goes for pool water. Pool water has higher concentrations of cholorine than normal drinking water and can be harmful to dogs.
There may also be other chemicals in the pool as well that may be harmful to pets. I know for our own pool we have a whole smorgasbord of pool chemicals other than just chlorine.
So to err on the side of caution, just provide your pet fresh water from the house. And don't worry if you dog happens to have a drink here and there from the pool, but just take it as a message that you are not providing him with other water options. Keep the small bowl of water you may provide him in a shaded area as hot water is not their liking nor helping them cool off.