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Checking For and Fixing Problems in the Sand Filter (or Glass Media Filter)

When opening or closing the pool, or a couple times per year, open the filter and check the filter bed.  Look for these telltale signs:

  • Low Filter Media:  The top of the filter bed should reach where the filter starts to curve inward.  If it is low, add new media to top it off to keep an optimal bed depth.  Low filter media will not filter efficiently and will cause persistent problems such as hazy water.
  • Dips in the Filter Media:  Check to see if there are dips in the filter media.  This could indicate a broken lateral which will also cause water issues.    Have the broken lateral fixed by a pool professional.
  • Gaps or Channeling in the Media:  Check for channeling in the media.  Channels can form through which the water flows, bypassing filtration.  If there is channeling (open pockets in the media along the side of the filter) do a deep clean of the filter.  If the media is sand, cover the media with muriatic acid and allow to sit overnight, backwashing to waste after 24 hours.  If the media is glass cover the media in regular household bleach and allow to sit overnight, backwashing to waste after 24 hours.
  • Bugs or Algae:  Check for bugs and/or eggs and larvae and algae.  The pool filter is a good breeding ground and insects or algae in the filter will cause a persistent problem of insects or algae in the pool.  To kill these do a deep clean of the filter using the same instructions above as for channeling.  For a bug infestation do another deep clean a few weeks later to kill any insects that hatched from eggs.
  • Large Debris:  Clean large debris off the top of the filter bed but do not over backwash the filter.  Allow for a 6-10 lbs pressure rise before backwashing (or backwash after 6 weeks, whichever comes first).  This allows fine debris to form a tight mesh on the top of the filter bed removing the smallest of particles from the water.    
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