Q–I purchased some splash blocks to set on the ground immediately below my downspouts. My wife thinks they are useless, but I believe they help divert water away from my foundation and water her gardens at the same time. She thinks that the roof water and the basement sump pump water should be piped away from the house. What do you think?
A–I’ll have to side with your wife on this one. The splash blocks are not entirely useless, however. They can effectively control erosion of the soil. The blocks can absorb some of the energy of the moving water before it hits the soil.
Rainwater that drains onto soil near your home is generally not a problem if you have sandy or very well drained soil. However, a large portion of the United States does not have well drained soil. Many people (including yours truly) live in regions that have clay rich soils and these soils don’t always drain that well. Their basements and crawlspaces can become indoor swimming pools in periods of heavy rainfall or sustained wet spells. Many people do not realize just how much rain falls from the sky in a moderate rainfall. For sake of discussion, let’s consider a normal ranch house that has an attached two-car garage. If the structure measures 30 by 66 feet and has a 2-foot roof overhang, there is 2,380 square feet of roof ready and waiting to catch rain drops.
A moderate, 1-inch rainfall will generate 1,483 gallons of water on this roof. This water will hit your splash blocks and enter the soil about 30 inches away from your foundation. If your region receives 40 inches of rainfall a year, you will inject about 59,320 gallons of water into your wife’s gardens. That might be a little overkill, don’t you think?
If your foundation currently is leak-free, your sump probably accepts a good portion of this water. If the sump pump discharge pipe merely dumps the water alongside your house, you end up recirculating this same water time and time again. This wastes electricity and leads to premature pump failure.
I believe that your storm water and sump water should be piped away from your house. Some urban areas allow this water to be connected to public storm sewers and water retention basins. If such a connection isn’t available at your location, pipe the water to the lowest portion of your lot where it would have drained naturally before your house was built.
Consider using SDR 35 or Schedule 40 PVC plumbing drainage pipe for this job. Install 4-inch diameter pipes in all locations. Use 90-degree elbows only at the base of downspouts. Use 45-degree fittings to change direction in all underground work.
Before you bury the pipes, take photos of their locations. These will come in useful as your wife’s gardens expand or if you have to make other excavations.
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Have questions about the remodeling process? Write to Tim Carter, c/o The Chicago Tribune, P.O. Box 36352, Cincinnati, Ohio 45236-0352. Questions will be answered only in the column.
For illustrations of several underground piping layouts, material lists and other tips on installing underground downspout drainage pipe, send $2 and your name and address to Tim Carter at the above address. Ask for Builder Bulletin No. 107.
