Certified Pool Operator Test 2025 – 400 Free Practice Questions to Pass the Exam

The diatomaceous earth (DE) filter is able to remove the smallest micron particles from pool water, typically down to 3-5 microns, which is finer than other common filter types. This exceptional filtration capability is due to the structure of the diatomaceous earth media, which consists of tiny, fossilized algae that have a highly porous surface. This structure allows them to trap even the tiniest particles, including most bacteria and algae, ensuring that the water is crystal clear and safe for swimming.

In comparison, while cartridge filters are effective, they usually have a filtration capability ranging from 10 to 20 microns, making them less efficient than DE filters for ultra-fine filtration. Sand filters are effective at removing larger particles, usually down to about 20-40 microns, and while high-rate sand filters can be beneficial for larger pools with higher turnover rates, they do not achieve the same level of micron particle removal as DE filters. Sump filters serve a different function entirely and are not specifically designed for swimming pool water filtration or for filtering out smaller debris.