Filter Balls / Polysphere

Filter Balls, also known as Polysphere, are a modern filter medium made from high-density synthetic polymer fibres with a fine microstructure. They are used as a replacement for traditional silica sand in the filtration systems of hot tubs, pools and cooling tubs. They work on the principle of mechanical filtration, where the fibrous structure traps solid particles and micro-debris as water passes through the filter tank. Compared to sand, they offer a significantly larger active filtration surface and lower hydraulic resistance. As a result, they can capture particles as small as approximately 3 microns, a considerably finer filtration than sand achieves. The material is lightweight, chemically inert and reusable after washing.

Advantages

• Significantly finer water filtration: They capture microparticles that sand lets through, resulting in visibly cleaner and optically clearer water.
• Lower operating load on the filtration system: Lower flow resistance reduces strain on the pump, which can extend its service life and reduce energy consumption.
• Simple handling and maintenance: Instead of handling 25 kg of sand, the material weighs only a few hundred grams and can be washed and reused.
• Longer filter medium service life: With proper maintenance, it can last several years without needing a complete replacement.

Filter balls and silica sand: a comparison

Filter balls are loaded into the filter in place of sand and change how it behaves in several respects at once. The table below summarises the differences that show up in everyday operation.

When filter balls are not suitable

The balls are not a universal replacement. In filters with a side valve and a large vessel diameter, the material can compress to one side and part of the volume is left unused. Likewise, in heavily soiled water the fine fibres clog faster than sand does. In both cases more frequent rinsing, or combining them with a coarser pre-filter, helps.

Related terms: Ozone generator, UV-C sterilisation, Balboa Water Group®.