What should you do if the top of the sand filter and the fingers at the bottom have both been replaced but there is still sand in the pool and you have already tried backwashing?

Many people mistake "mustard algae" as sand in their pool. Does the sand briefly disappear when you run a pool brush over it? Mustard algae resettles quickly and looks very much like filter sand. We have helped many customers with this problem. Also, if there is truly sand in the pool and you have replaced the laterals, check for any leakage of air around the filter. You may hear or see cavation in the pump when it is shut off.