Sand filter just won't backwash

[blsylvia]

Ok - so I have a couple of problems going on.

1. Pressure is about 8-10 PSI lower than it should be.
2. Water leaking from backwash port.
3. Multiport valve seems to not want to set to backwash or rinse. It doesn't seem like the sand is doing anything when set to these cycles.

For the pressure I have checked every hose for leaks and there are none. I have checked the pump for debri, inspected the o ring, checked the impeller. Nothing.

I took apart the multiport valve and see that the spider gasket is worn so I will replace that today and that will fix the backwash leak.

Could the falty gasket be the reason I really can't change the cycles? Something in the handle of the valve just seems wrong. I looked in the filter and the water is filthy, but when I backwash It comes out slower but clean, and there is no pressure pushing the dirt through the site glass. I seems like the filter is not really working and the water is just bypassing the sand.

Could this be the gasket or is there a bigger problem?

Thanks - Jen