I have a sand filter, and I've always had a feeling it wasn't doing it's job very well. I frequently have to vacuum to waste because it has never seemed to be filtering out anything. I slammed for almost 30 days last time before trying a flocculent and vacuuming to waste. While I know that the fact that there is any algae to begin with is my fault/water chemistry, I would still like my filter to work. After my 30 day SLAM i took my filter apart and realized my stand pipe was cracked. So I bought a new stand pipe, replaced the sand and started fresh. Except....I'm still pretty sure it isn't working. I know it isn't working because earlier I shocked and was vacuuming (not to waste, through the filter) and I watched what i was vaccuming shooting right back into the pool through the return jet. I really don't know what the next step is. Help? please?