I have a Hayward sand filter with the multiport valve at the top.
My pump motor went bad, and my pool was down for a week and a half before I got the new motor installed. The pool is dark green. I backwashed the filter - water in the sight glass was white as usual. After it cleared, I turned to rinse for a minute or so. Finally, I turned the valve back to the filter position. When I turned the pump back on, water was spewing from the clamp joining the valve to the body of the filter. The leaks shoot out right where the two bolts are. I tightened the bolts until I was afraid I might break something, but the leak persisted. I loosened them again and tried gradually tightening, but the leaks don't improve.
Note that the new pump motor is slightly more powerful than the old - I will give details if anyone thinks that's important.