Selecting the correct technology depends on the specific problem you are solving. For electric tank heaters, prioritize polyphosphate or siliphos filters to prevent scale buildup on heating elements. For gas tankless heaters, high-flow stainless steel mesh pre-filters are essential to prevent sediment from clogging narrow heat exchangers. If the goal is skin protection, look for KDF-55 or Calcium Sulfite media, which are highly effective at removing chlorine and heavy metals in high-temperature environments.