Most people like around 50. Some places that are extremely hot and sunny seem to be better with it a little higher. But, I'd start with around 50ppm. If you find that you are having trouble maintaining adequate chlorine levels throughout the day, you can always bump it up later. Just remember to keep your chlorine in the proper range for whatever CYA level you have so you can avoid algae. (Take a look at the Best Guess Chlorine Chart in my signature below for the correlation between CYA levels and needed chlorine levels.)