Having a bunch of people swim can cloud your pool multiple different ways, some of which do NOT indicate any problem. For example, heavy use of sunscreen will do it for sure.

But, one of the problems that result from the use VS pumps is that they are almost ALWAYS too big for the filters they are paired with and can CAUSE poor filtration!

With sand filters, this has 3 major effects:
  1. If you backwash on high speed . . . or even fairly high speed . . . you will blow sand out of your filter every time you backwash. If your filter is 24" or less, this has likely already been happening. AND, reduced sand = poorer filtration.
  2. Also, if you don't match flow to filter, your BIG pump will force dirt THROUGH your little filter.
  3. Finally, people often think INCREASING pump speed will IMPROVE filtration, and sometimes do this after heavy bather loads. But the OPPOSITE is true, per #2 above!