To achieve the best drainage capacity for artificial grass, both the turf and base are equally important: all our turf products have the drainage capacity at an average of 50-60 inches per hour which can handle the most downpour you can imagine, in order to achieve its best level, the base will need to be able to handle the similar amount of water. We recommend to have the base built as thick as 4” with 2-1/2” of drain rock with 1-1/2” of top layer, this is especially important for rainy areas. Some of the less rainy areas, people might do thinner base. The golden rule for artificial grass drainage is that the turf will drain just as well as the base. Please feel free to contact us if you have any other questions by phone: 877 796 8873 or email: [email protected], thank you.