Quote Originally Posted by CarlD View Post
BritinUSA:


But I believe N2 recommends you change the cartridge every 6 months or every season, which ever it shorter. You are using yours for 2 seasons so you have ALREADY cut your costs in half by breaking "the rules" --not that you shouldn't--if you have been successful with 2 seasons per cart you've already gotten ahead of one of the objections to the N2 system.
Carl,
by 'breaking the rules, they do not have sanitized water! Period. Remember the pool is oing to look clear because of the copper sulfate in the cart but the N2 also depends on silver nitrate. The reason the EPA approved these units is because they are replaced every 6 months of use. That is two carts a year (or one if the pool is closed for 6 months or longer). Once the cart is "activated" it does not have an indefinite shelf life.