We filled our pool with water last night, put the salt in it this morning, once the salt was dissolved, we started it up. For about a minute it worked fine, and then gave a Code 90 "Low Flow" Error code. I could see there was a little air trapped in the hose. We turned off both systems, and purged the air from the lines on our Krystal Clear 637R pump. That did it. We turned everything back on, and it didn't give the error code. Somewhere between hour 2-3, it gave the error code again. Purged the lines again, turned it back on, and fine. Now, it gives the error code every hour on the hour. So, either for some reason we are getting too much air in the lines, or that isn't the problem, although it seems to fix it for a short time. Any suggestions?