Usually this means your water is acidic. This is caused first and fore most by the rain, all secondary would be swimmer waste (perfumes, lotions, insect repellant, deodorant etc). This could create a very big problem for your pool equipment as well as feeling horrible on your skin. Your water is probably crystal clear and unfortunately clear water is not always good water cause acid is clear too. Not a huge thing unless you have left it for a while and it has eaten the heat exchanger out of your heater. If this happens you are into another problem altogether. Come in and see us chances are all you need is some Balance Pak 100 which is used to raise your total alkalinity, which in turn will raise your ph. You will find a huge difference in your water after putting this product in, as well you will see a big difference in bather comfort.