We've had a 24' above ground for about 15 years now. Over this time I have "experimented" with multiple setup. The last couple of years I've been using a sand filter (second hand given to me) . This spring I was gifted a new sand filter (Blue Devil) which came with the multivalve. I also purchased a new variable speed pump. I've set it all up and things seemed to be ok. I had some algae this year as always and proceeded to treat the pool and vacuum the pool as usual. After the process I started to backwash the filter. To my surprise, the flow out of the backwash hose was really low compared to what I am accustomed to seeing. Also the water was not discolored at all, no green or brown coloration. Over the next week I back washed several more times each time low flow and no discoloration. The site glass contents is clear as well. It's almost as if the water is not passing thru the filter at all but just being recirculated back into the pool and the debris in the pool remains. Something else to mention, the pressure gauge never changes, it stays on 0. I have changed the gauge with the same results no matter the setting of the valve. Low flow on backwash and rinse but strong flow when on filter and recirculate. Starting to think the value is messed up. Multi valve pic attached. Any ideas? Thanks