Due to evap and splash out, my water level is down an inch or so below where the pool installers told me to keep it, and it got me to thinking about adding water. When should you normally replace the loss? My water source (city water) tends to be brown at times, so is there a way to fill through the filter system? I know it won't clear it completely up, but it would help, being as it would only be 500-1k gallons.