Backwashing Your Sand Filter
BACKWASHING YOUR SAND FILTER
Sand filters must plug and have pressure rise on their gauge to remove small particles from the pool. A functional pressure gauge is necessary to successfully operate the pool. Pools with 1970 to 1980 slide valves instead of multiport valves should upgrade the slide valve to a 6 way multiport as their most cost effective pool purchase they can make.
Without a rinse feature the slide valve is incapable of removing algae spore, phosphate, and human cells from water. Many slide valve owners report “dog breath” odors near their filter or eventually in the entire pool.
Backwashing the pool should occur after 6 lb pressure rise on the gauge and prior to a 10 lb rise over starting pressure. The starting pressure must be recorded after a proper backwash. The gauge can be marked with a waterproof marker so any pool professional or family member will know the operating status of your filter.
The proper method is 2 minutes backwash followed by 30 seconds rinse AND a second 2 minute backwash followed by rinse to clear in the small site glass at the top of your filter. YOU MUST TURN THE PUMP OFF between each movement on the multiport valve or you will damage the “spider” o-ring inside the valve. The multiport valve should easily and distinctly lock into position.
When finished with the second backwash/rinse cycle the pump should be turned off and the valve returned to the “filter” position. The pool should be operating at your starting pressure. The “recirculate” and “waste” settings are covered under “Problem Solving” and vacuum chapters of this book.
Backwashing too frequently will result in more chemical use and less water clarity with a sand filter, especially if zeolite or glass media is used. Any sand filtered pool that has gone four weeks without a pressure rise should backwash the pool regardless of pool clarity.