We have an 18,500 gallon inground vinyl pool with a SWG. This is our first season with a SWG. The water has been testing fine all summer until recently. We are having problems keeping the FC in the recommended range. We have to add chlorine regularly and that is the only way it has come up to 3. Here are the current numbers. Any suggestions as to what to do to keep the FC up most of the time?? The SWG is now running at 80%. The pool gets direct sunlight most of the day.