Chances of catching AIDS or other infectious diseases while swimming in pool?

I have taken up an interest in swimming in the past few weeks. One thing that still bothers me is getting AIDS from people I swim with. In my pool, there is no chemical that detect changes in pH level so I can't really tell if someone urinates or not when I swim. How long does it take for chlorine to kill the HIV virus or any other type of disease causing organisms? When I swim, I usually swallow some water so this worries me.