The decision of how long to leave the chlorine tablets in the pool depends on a variety of factors, including water temperature, pH levels, and the type of disinfectant used. Generally speaking, you should leave them in for at least 4 hours (or as specified by your specific disinfectant). However, it is always recommended that you test the water before heading out and make sure that it is safe to swim. If there are any concerns whatsoever, please contact your local pool manager.