Pea gravel - per 25kg
Pea Gravel is more common in commercial pool and spa filters due to the higher bather load & greater requirement for performance from the filter media. Ideally there should be no more than a 1" layer pf pea gravel over your lateral system. The specific reasons for the installation of pea gravel is:
Gravel helps support the laterals from the weight of the sand
Gravel will filter out the sand from the water before reaching the lateral system
Gravel will help eliminate anaerobic bacteria from forming underneath the lateral system
Gravel provides more open area for a smoother flow of water after it has passed through the sand.