Houses should last for a long time, with as little maintenance as possible. One of the best ways to keep your house in great condition is to limit its contact with water. Though houses are built to repel water, it's always best to keep water away in the first place.
Roof water runoff collected by gutters is sent down the vertical downspouts. When the water exits the downspouts, it needs someplace to go—other than pooling around the house foundation. For some homeowners, this pooled water is left to hopefully find its own route away from the house. Other homeowners, at best, attach plastic extensions that move the water an additional 4 feet beyond the foundation.
Extensions are helpful but not adequate, especially if you live in a wet climate like Hawaii, the Pacific Northwest, Florida, and areas of the Northeast. In these areas, you need a comprehensive solution to all of your roof water runoff that takes water from the point of contact—the roof—to an endpoint as far away from the house as possible—often, near the property line.
That solution, which adds value to your home and eliminates roof runoff concerns for good, is called a catch basin drainage system.
A catch basin is a buried container for receiving and re-distributing surface water. The open top is covered with a slotted grate to allow water to pass through while blocking leaves and other debris. On the sides of the basin are holes for attaching pipes that move the water away from the basin.
How a Catch Basin Drainage System Works
Unwanted water around the home creates problems. Water promotes mold growth, rots out wood, turns your lawn into moss, and welcomes insects into your home. Sustained periods of water will eventually create major damage, requiring expensive repairs.
A catch basin collects that water and, for most of its journey, invisibly shuttles it away from your house through buried pipes to a spot where it cannot harm your house. That journey begins on the roof:
- Roof: Rain or snow contacts the roof and runs down to the gutters.
- Gutters: Gutters move the water horizontally to downspouts at one or both ends of the gutter.
- Downspout: Water from the gutters moves vertically downward through the downspouts.
- Catch Basin Grate: Water exits the bottom of the downspout and runs through the catch basin's top grate.
- Catch Basin: Water rises in the catch basin until it reaches the exit pipe.
- Pipes: Buried 3-inch or 4-inch pipes running on a decline carry the water away.
- Exit Point: Water leaves the end of the drainage pipe, soaking into the ground or flowing away.
- Catch Basin Drains Off: Back in the catch basin, tiny weep holes slowly drip out standing water.
Planning the Catch Basin Drainage System
Identify the start of the drainage system run—the catch basin location. If the starting location is near a downspout, the catch basin will be located about 12 to 18 inches from the foundation, depending on the size of the catch basin.
The end of the run should be at least 10 feet away on a decline and farther for flat ground. Move the water as far away from the foundation as possible.
The pipe should have a 0.25:10 decline or greater (1/4-inch per every 8 to 10 feet). If the pipe is running down a natural slope, then you can likely dig the trench to a uniform depth. If there is no slope, then you will need to decline the trench.
Equipment / Tools
- 1 shovel
- 1 trenching shovel
- 8 string and stakes
- 1 hammer or mallet
- 1 caulking gun
- 1 electric drill
- 1 set drill bits
- 1 catch basin
- 3 PVC sewage pipes, 4-inch
- 3 bags drain gravel
- 2 packs plastic sheeting
- 1 tube silicone caulk
Building the Catch Basin Drainage System
Dig the Catch Basin Hole
Dig a hole for the catch basin to the depth of the basin plus another 6 inches for gravel. Add the gravel.
Dig the Trench
Stake out the area to be trenched with the string and stakes. Then, use the trenching shovel to remove the turf and to dig the trench from the catch basin to the intended exit point. Toss the soil on a plastic sheet to avoid adding dirt and mud to the lawn.
Store Dirt Under Plastic Sheeting
Mound up the dirt from the trench under plastic sheeting. Close up the sheet at the end of every workday.
Run the Pipe Through the Trench
Once you have dug the trench to at least 8 inches deep, lay the 4-inch sewer pipe. Extend the pipe as far as you need.
When connecting bell-end sewer pipe, the female end of the pipe (the bell) must be pointing up-grade; that is, in the direction of the catch basin.
Pour Gravel Around the Entry Point of the Basin
Concentrate much of the drain gravel under and around the catch basin. Also, have a bed of gravel along the first foot or two along the drain pipe.
Push the Pipe Into the Side of the Basin
Gently twist the 4-inch pipe into the side of the catch basin and through the flexible sleeve. Other types of catch basins have a grooved ring. The end of the pipe sits in the grooved ring and is sealed with silicone caulk.
Pull the Pipe Into the Basin
On the inside of the catch basin, pull the pipe inward. Make sure that the pipe extends about 3 or 4 inches. Do not have the pipe enter the basin flush with the side of the basin.
Catch basins and pipes should be fitted tightly so that they are as leak-free as possible. However, some leakage is expected. This is not a pressurized system where no leakage is required. The PVC pipes do not need to be cemented.
Drill several weep holes at the bottom of the basin to prevent water from pooling.
Install a Pop-Up Emitter at the End
At the end of the pipe run, add at least 6 inches of gravel below the end of the pipe. Insert the pop-up emitter and its self-closing cap.
Build a Barrier Around the Drain Emitter
A barrier around the drain emitter is not mandatory but is helpful since it keeps the gravel in place and provides a barrier against lawn and weed growth. A simple barrier can be built from one-by-eight pressure-treated lumber to a size roughly 18 inches square. Cut a half-circle into one side (at the bottom) so that the barrier can rest on the pipe.
Add Gravel Around the Emitter
Slowly pour gravel around the pop-up emitter to just below the level of the emitter's lip. Always keep the cap clear because frequent cleaning of the elbow joint is necessary.
Backfill the trench and around the catch basin with gravel, sand, or dirt. The more gravel you can use, the better. Gravel helps water drain away faster.
When to Call a Professional
Building a yard drainage system is not complex, but it does involve a lot of earth-moving. Professionals have trenching tools that speed up the process and eliminate much of the hard labor. For more than one or two runs of trenched drainage pipe, you may want to call a professional for help.