I've had the 18' donut pool for 2 years now...bought it used off a friend who had it for a few years and its still going strong. We have the original pump but instead on using the cartridge we hooked up a Hayward sand filter to it because we have well water and it helps to filter out the iron alot better. Which bring me to this...I've filled my pool for 2 seasons now off my well water which has ALOT of iron and I've managed to clear it up. I use a metal remover at the begining of the season and its great!

Good Luck to you and the kids!