We opened our pool about a month ago and all seemed well. We had the salt water generator cleaned this year and the pool is about 4 years old. I noticed that the flow into the pool was not as strong as it typically was and that there was a small air pocket in the pump basket. I back washed and the pressure went back to normal. However I noticed that there was a bunch of air blowing back into the pool after the backwash cycle. This keeps happening every few days. The last time this happened I tried to bypass the filter by putting it in recirculate and the pressure went to normal but again their was air coming out of the returns for a bit. I'm guessing this is a problem with the sand filter but is it typical to get the air bubbles too or does that indicate a new problem. The air entering the pool lasts for about 20 to 15 seconds. We have never had an algae problem and the backwash water has been clean. Thanks.