Pentair Multiport valve SM 20-3 disharging water to backwash

I backwashed due to alot of rain. When I tried to put the valve back in filter, it is still disharging to the backwash.

I wanted to take the valve apart and was looking for advice.

It is on a pentair tritonII commercial filter with crushed glass. The valve is model SM 20-3, valve assembly SM2-PP2 and it is a couple years old.

Probably, a blown out or damaged multi-port gasket

#10 on image below:

http://www.pentairpool.com/images/pr..._prts_webL.gif