Pea Gravel for Sand Filters

The primary purpose is to prevent chanelling in within sand filters. Without it, water will create 'channels' through the sand bed from top to bottom, effectively bypassing the filtering process. Pea gravel will typically cover the lower laterals and force the water to actually filter through the sand bed.

Ultimately, this depends on the exact model of filter you have. On your sand filter, you will see the manufacturers' recommendations for media required. Smaller, residential filters may not call for pea gravel, but always consult your filters' specifications.