Our old sand filter gave up... so I asked around ... the pool guys wanted to sell me a larger 4 cartridge filter for $1200. Then I asked a neighbor about his ... he has a 13000 gallon pool and 3/4 horse pump and this filter and has never had a problem . I have a 26000 gallon pool and 3/4 pump... this filter works amazing... my pool guy said it was too small, he is full of hot air because my return pipe is only 1 1/2 inches in diameter and you cannot push more than 60 gallons per minute through a 1 1/2 inch pipe anyway... no matter how much horsepower you have so this filter is perfect for my pool, it was very green and took two days to clear up after we replace the sand filter with this new cartridge filter... you just have to wash the filter out a little more often than you would with multiple cartridges. It’s very easy to wash the cartridge out. Whenever somebody wants to sell you something that’s bigger, ask them why and what the benefits are because if you only have a certain size return pipe only a certain amount of water can circulate through it no matter how large the filter is.