When I switch my pump into high speed, it looks like there is dirt shooting through the returns for about 5 seconds. I only use high speed for priming the pump after cleaning the strainer basket, and sometimes for vacuuming. The filter does a great job keeping the water sparkling clear, even with the considerable amount of debris I get in the pool. I'm not sure when the sand was last changed, if it ever has. Is there anything I should try before removing all the sand and inspecting the internals?