A common water problem in the Northwest
Downspout drainage is always the first place to look if you have water entering your basement or crawl space and one of the easiest problems to address. There are many factors that can lead downspout systems to fail but debris from your roof and gutters is the usual source of problems. There are various gutter filters available to help prevent debris from entering the system. If your system is already clogged, it is sometimes possible to washout the downspout system but if the system does not “daylight out” (a point for water to freely flow out) then there is most likely a dry well or dispersion trench to contain and disperse the water captured from your roof.
When debris is the problem with your drainage system, it is often too late to clean out the system. We find that most drainage systems do not have a catchment system to collect debris and silt before they make it to the drywall. The graphic on this page shows a simple and inexpensive catch basin that works in multiple ways to protect and improve your drainage system.
The first benefit on an engineered system is a sump to collect debris before it can reach and clog the dry well or dispersion trench. Solids will drop to the bottom of the catch basin where they can be cleaned out as needed and the water will flow freely out to the dispersion system. To add further protection, a filter can be placed on the outflow of the catch basin to catch floating debris such as leaves.
The second benefit of an engineered system is the catch basin will serve as an overflow moving water away from the house during periods of extreme rain when the dispersion system is overwhelmed. In most cases, we see old systems that are clogged and only function at a very reduced capacity and with out the catch basin to overflow water to a strategic spot. Without overflow management, the water will back up to the house where all of the captured roof water is often times channeled directly to the foundation.
How much rain water does a roof collect? To give you an idea of the amount of rain that your system needs to be capable of managing, a 1 inch rain fall equals 1,200 gallons of water for a 2,000 square foot roof. Through out the winter months it is common for us in the Olympia area to get up to five inches of rain per month.
That could add up to 6,000 gallons of water per month that your yard needs to effectively manage to stay out of your house!