Dino,

Check past threads on downspouts. I remember there being quite a few. Is your question concerning the material of the downspout or where the downspout disposes of the water in relation to the house's yard? Aloha

I meant what's the best kind to get bi bought 4' black ribbed hoses that are 8 ft in length. How short should I trim them?

D,

If you used polyethylene ribbed drain line then you wanted to get the water away from your house slab. The important factor is where do you need the water to flow and then get it to the street or City drain system off your property. Three options that vary in costs. Sheet flow over the ground which flow into shallow swales to the street(usually across sidewalks) is easiest and less costly but depends on yard slopes and yard drainage patterns to the street. Option two is an underground system of piping to the street usually out through the street curb or directly to a city street drain outlet box. Again it is dependent on the yard sloping away to the street. This option give invisibility to your roof drainage water but has higher installation and maintenance costs. The third option is the costliest but has additional benefits of using the water in your garden or to the street. This option is a sump/cistern with a submersible sump pump with auto float valves or delayed timer start up feature. This option will also have piping but moves water where you need or want it to go. To actually answer your question, the diverter pipe needs only to be about two feet away from your house slab which allows sheet flow across the lawn or into the flowerbed. Usually downspouts are fiberglass or concrete diverter slabs that creates a sheet-flow away from the house. They are about 24" long and are not as visible(lower profile) as the ribbed pipeline. JMHO Aloha