We all know that downspouts from eavestrough should be re-directed away from our foundations. The volumes of water that come off a roof can be quite substantial during times of rain, when you consider it will be concentrated at the discharge point in two or more corners of the foundation.
The main challenge with this is that if there are any defects in the foundation such as cracks, tie holes, honeycomb in the concrete etc., in this vicinity, water may enter through. It is important to have these defects repaired in your foundation. Once these items are repaired, then the next step is to re-direct the downspouts.
This will keep as much water as you can away from the repaired areas which is very important, especially given that some defects could be below grade or so small they are almost hidden from view and can easily be missed. The large volume of water that comes from a downspout can seep through the ground forming paths or fissures. The long this goes on, the more the ground erodes causing them to be larger and wider.
The problem with this is that the water makes its way down to the footing drains, and brings soil right along with it, speeding up the rate at which the drains will become silted up. If they are already silted up, the excess volume of water will only add to the hydrostatic pressure thus forcing the water between the wall and footing and up onto the floor inside the house.
The little attachments and pieces of eavestrough or ABS often used by homeowners to redirect often look like a eight to ten foot section of pipe or eavestrough running away from the house. One way to eliminate unsightly sections of pipe and re-direct the flow away from the exterior wall is to direct the flow away by grading the soil away from the foundation and making sure it slopes away from the house.