In a biguinide pool carts need to be cleaned weekly, soaked monthly, and replaced yearly. It's not the cart, it's the buguinide. In a chlorine pool carts need to be cleaned every month or two (actually many can go much longer before a pressure rise but I would recommend cleaning at least every 2 months to make the cleaning job easier) , they need to be soaked yearly, and can last up to about 5 years with proper care. Sand does not fare much better in a biguinide pool with the biguinide manufactuers recommending monthly sand cleaning and yearly replacement of the sand! Biguinide works by causing the bacteria to literally explode and this forms a gooey substances that is sometimes referred to as 'baquagoo'. The biguinie is a polymer and this causes this stuff to clump together, much like a clarifier or floc would. This is what is clogging up the filter. With chlorine the bacteria are oxidized (burned up) and this does not happen.