X10 Filter - 12 inch Inline KDF / Carbon FilterThe tap water, well water, and lake water used to fill a hot tub is probably not as pure as you think. Impurities such as copper, calcium, sodium, iron, mercury, and other heavy metals can be harmful to bathers, can harm your spa parts and make it harder to balance your hot tub water. These deposits can seriously harm your heater element, jets, pump and spa shell. These deposits will also make it difficult to balance your spa water and can impair