A 13,500-gallon pool is the most common volume for 24' round above ground pools. To maintain clarity, you need a 28 GPM flow rate. We recommend the Black+Decker 1.0 HP Dual Speed pump paired with the 300 Series Cartridge Filter. This 'sweet spot' combination allows you to utilize the low-speed setting for energy-efficient daily filtration, while the high-capacity 300 Series filter ensures you aren't constantly cleaning cartridges during the peak of summer.