I've been doing business with Leslie's Pool Supplies for many years. Every time I go in there I'm blown away by how knowledgeable at the staff is. The customer service here is one of the best I've experienced. They make sure to educate their customers and fix whatever problem they might have.
They will check the chemicals in the pool and also inspect and repair your pool vacuum as well free of charge. Leslie's Pool supplies might be a little expensive, but they constantly offer coupons and rebates. They also recently started their own rewards so sign up if you're interested. So if your pool needs some good TLC I'd recommend coming to Leslie's. The end.