Bad Smell in My Pool's Sand Filter

Change the Sand

• The sand inside the filter does not last indefinitely. The jagged edges of the sand catch and hold the debris that the pool water has collected, and regular backwashing flushes out this debris. However, over time, backwashing becomes less and less effective at removing all the debris from the sand, and the sand itself should be emptied out and replaced with new sand. Under normal pool use conditions, you should change the sand every three to four years, although you might even need to do it more often than that. Consider replacing the sand with new sand especially if the sand filter has a bad odor.

Chemical Filter Cleaner

• In addition to all the larger debris that collects within the sand, smaller pollutants such as oils, minerals and grease also accumulate inside the filter. While backwashing the filter removes the larger debris, these oils and other contaminants often stay behind, and this might cause an unpleasant odor. To get rid of these additional contaminants, add a liquid sand filter cleaner, following the manufacturer's instructions. Normally, you pour the chemical into the pool skimmer before you backwash the sand filter.

Pool Water Testing

• Another possible source of the bad sand filter smell might be dirty or unbalanced pool water. You should test the pH and chlorine levels in the pool water regularly -- normally at least once a week -- to determine whether they should be adjusted. Also, test the water after backwashing the sand filter. Obtain a trustworthy pool test kit from a local swimming pool supply company and test the water yourself. Or, scoop out some of the pool water and take it to a pool supply store and have a store employee test the water's current levels for you.

Preventive Maintenance

• The two main parts of proper swimming pool maintenance are keeping the water's chemical levels balanced and keeping the water clean of foreign materials and pollutants. Because the pool pump moves the water through the sand filter each day, carefully monitor the pressure reading on the filter, so that you can backwash it when needed. Pay particular attention after a lot of swimmers have used the pool at once, and backwash the filter regularly to prevent loss of filter efficiency and the bad smell from returning.