I just recently had a new sand filter installed (which was a nightmare because of the repair guy), and after I got everything running, it appeared to be running well. After a few hours the pressure jumped from approximately 15 PSI to 35 PSI. I backwashed and rinsed and it appeared to fix the problem. The pressure jumped not long after the backwash, so I turned the pump off and ensured everything was tight. When I turned the pump on, the pressure was back to normal. Long story short, whenever the pressure jumps, all I have to do is turn the pump off for a minute and the pressure returns to normal. Any ideas on what could be causing this?