Spa METALfree is a highly effective metal deactivation agent that prevents staining and discoloration from trace metals such as, iron and copper. These trace may already be in the spa fill water or in water added to maintain water level. Spa METALfree should be used as part of a well designed weekly spa maintenance program. Various metals like iron and copper are frequently found in domestic tap water. These metals can build-up and lead to staining on spa surfaces. Due to regular topping up of spa fill water, it is recommended to dose weekly with Spa METALfree. Spa METALfree does not contain phosphonic acids and will NOT raise phosphate levels in spa water.