AquaTools Pump/sand filter question

[s0undone]

We just installed a 24,000 gallon AG pool. Filled it with well water so there is no visibility. We've shocked it and had the filter running for the past two days. We backwashed today . When we attempt to use the vaccume to get the sediment off the bottom it goes through the pump-filter and jets back into the pool as dirty water. What gives? We have a 400lb sand filter with a 2.5hp 2 speed pump. Any advice on how to get the water cleared up and why the filter seems to be failing even when it's freshly backwashed and rinsed? Help!

Thanks,
Dena