With a cya of 60 you need to get your chorine up to 20ppms to reach shock level. I wouldn't swim in the water if there is combined chlorine, that means something is in the water that needs to be killed. You will need to get the chlorine up to 20ppms and hold it there until the chlorine holds overnight. Once your have no combined chlorine, it is ok to swim in the pool even with the chlorine at 20ppms. Read through this thread, especially chem geeks answer:

http://www.poolforum.com/pf2/showthr...3230#post33230