Jawman and Dave, don't be so quick to ignore him, the pool dude might be onto something. Without the cartridges in, the pool is running on 'recirc', the water is moving and the chems are getting spread arround. It also allows Jaw to 'vac to waste' by opening the drain plug and attaching a hose to it. Let the bleach do it's killing and get the debris out without having to clean the cartridges, providing that water to refill the pool is not a problem, at least this guy has given it some thought, I'm sure that the fact that I've suggested the same thing here isn't influencing my response at all Jaw, however you handle it, I hope you have a great summer with your pool once the algae is gone!!