A basement drain should be put into a concrete block wall while the home is under construction. It can be done afterward to upgrade the home at much higher cost and labor. Follow these directions to install an exterior or interior drain through a concrete wall.
Step 1 - Determine the Drainage of Your Home Site
If your home is on the highest elevation of the lot, an external drain will work well to keep your basement dry. If your home site has little slope or is on top of a high water table, you will need to install an internal drain with a sump pump.
Step 2 - Take Measurements to Install External Drain
You can install this type of drain from an existing basement, although it should be done immediately after the concrete block foundation is laid. Measure the perimeter of your basement walls. Your external drain pipe will go all the way around it, and out at least 40 feet away from your house. Slope the drain pipe leading away from the house 1/4 inch for every 4 feet of length. Purchase the length of 4 inch pipe you will need. Use 6 inch diameter pipe if the drain system will extend more than 100 feet from the house.
Step 3 - Dig, Line and Partly Fill the Drainage Trench
Rent a backhoe for a weekend and dig the drainage trench. It should go down to the bottom of the foundation from the ground surface, and should be 12 inches wide. Flatten the bottom of the drainage trench so it is level. Line the trench and up the concrete wall 6 inches with the filter fabric. Place a 3 inch deep bed of coarse gravel in the bottom of the trench. You will lay the pipe on top of this gravel bed.
Step 4 - Install the Drain
Use the hole saw to cut a 4 1/8 inch circular hole in the concrete block wall. Feed the pipe through the hole and run it all the way around the foundation. Seal off the drain hole in the wall with poured cement and caulking.
Step 5 - Finish Filling the Trench
Add 8 inches of coarse gravel above the drain pipe all the way around the foundation. Pull the filter fabric over the gravel and tuck it in against the concrete wall. Finish filling the trench with coarse sand to a depth of 6 inches. Put garden soil over the sand and plant with grass seed or lay lawn sod.
Step 6 - Install an Interior Drain to a Sump Pump
Under the basement floor, pour in gravel to a depth of 8 inches to allow soil drainage. Make a very shallow basement and cut the drain hole in the concrete right at floor level. Cut an 18 inch square sump pond in the basement floor to catch the sump water. Install the sump pump on the edge of the sump pond, and attach a battery backup so the pump will work if the electricity fails.