How Do You Lower CYA?

[waterbear]

It can take a very long time for the CYA to go down on it's own, expecially if you have a cartridge filter. CYA will only go down by dilution under normal circumstances. This means refilling from splashout, backwashing a filter, or draining and refilling. Evaporation will merely concentrate it and it will dilute to where it was before when the evaporated water is replaced. Using bleach or any other non stabilized chlorine will not make it go down. However, using trichlor or dichlor will make it rise since with every use of these products you are adding more CYA!

BTW, most powdered shock is Cal Hypo (calcium hypochlorite) and is non stabilized chlorine. Dichlor is ususally only recommended for shocking spas which get drained and refilled every 3 months. It is ususally used in poos for normal sanitation.