What is an underground gutter drainage system?
An underground gutter drainage system is a network of pipes buried beneath the ground that collects rainwater from your downspouts and directs it far away from your home’s foundation to a safe discharge point. Unlike surface extensions, these systems are concealed, providing superior aesthetics and more effective water management for your property. They prevent water from pooling around the house, which can lead to foundation issues, basement flooding, and landscape erosion.
Benefits: esthetics, foundation protection, water management
- Aesthetics: The primary visual benefit is the elimination of unsightly splash blocks or flexible extensions, keeping your landscape clean and uncluttered.
- Foundation Protection: By channeling water significant distances away, underground systems offer superior protection against hydrostatic pressure buildup, foundation cracks, and basement leaks.
- Efficient Water Management: They handle large volumes of water effectively, even during heavy downpours, preventing pooling and directing water to designated areas like dry wells, rain gardens, or municipal storm drains.
Choosing the right pipes and materials
The choice of pipe material is crucial for longevity and performance:
- PVC (Polyvinyl Chloride): The most common choice. It’s rigid, durable, smooth (resists clogging), and easy to work with. Available in various diameters (4-inch schedule 40 PVC is typical).
- Corrugated Plastic Pipe (Flexible): More affordable and easier to install around obstacles due to its flexibility. However, its ribbed interior can trap debris, making it more prone to clogging. Often used for shorter runs or when flexibility is paramount.
- Perforated Pipe: Used for French drains, allowing water to slowly dissipate into the ground along its length. Not suitable for direct downspout connection if you need to move water quickly to a single discharge point.
Calculating pitch and length (10 ft away rule)
- Pitch (Slope): A crucial aspect for effective gravity-fed drainage. A minimum pitch of 1/8 inch per foot (or 1 inch drop per 8 feet of run) is recommended to ensure proper water flow and prevent standing water that can lead to clogs or freezing.
- Length (10 ft away rule): As a general guideline, the discharge point of your underground system should be at least 10 feet away from your home’s foundation. This ensures that water is released far enough away to prevent it from seeping back towards the house. However, local codes or specific site conditions might require even greater distances.
Step-by-step installation guide
Excavation & trenching
- Mark the Trench: Map out the path for your underground pipes, extending at least 10 feet from the foundation. Use spray paint or flags.
- Dig the Trench: Excavate a trench that is deep enough to accommodate the pipe (typically 6-12 inches deep, below the frost line in cold climates) and wide enough to work in. Remember to maintain the calculated pitch along the entire length. A string line level can help.
Laying pipe and bedding
- Add Bedding Material: Lay a few inches of gravel or crushed stone at the bottom of the trench. This provides a stable, level base and aids drainage around the pipe.
- Lay the Pipe: Place the pipes in the trench, ensuring the correct pitch is maintained. Connect sections using appropriate fittings and PVC cement if using rigid PVC.
- Backfill (Partially): Once the pipe is laid, partially backfill the trench with gravel or the excavated soil, compacting it lightly around the pipe to hold it in place.
Connecting downspouts
- Downspout Adaptor: Install a downspout adaptor at the base of each downspout where it enters the underground system. This typically involves cutting the downspout to the correct height and securing the adaptor.
- Seal Connections: Use silicone sealant or PVC cement to ensure watertight connections between the downspout, adaptor, and the underground pipe.
Outflow termination options
The end of your underground system needs a proper way to discharge water:
- Pop-Up Emitters: A common and discreet option. A spring-loaded cap pops open when water pressure builds, releasing water onto the surface, then closes when drainage stops.
- Dry Well: A buried, gravel-filled pit that allows water to slowly dissipate into the surrounding soil. Ideal for properties with good drainage.
- Rain Garden: A shallow, landscaped depression designed to collect and absorb stormwater runoff, often featuring native plants.
- Street Storm Drain: If permitted by local regulations, connect directly to a municipal storm drain system.
Preventing and fixing common issues
Clogging
- Prevention: Install downspout filters or gutter guards to prevent debris from entering the system. Ensure adequate pitch.
- Fix: Use a drain snake or flush with a garden hose to clear blockages. For severe clogs, sections of pipe may need to be excavated.
Root intrusion
- Prevention: Avoid planting trees or shrubs with aggressive root systems near the drainage lines. Use solid (non-perforated) pipes.
- Fix: Root-killing chemicals (use with caution and research) or professional root removal with specialized equipment.
Frost and pitch errors
- Prevention: Bury pipes below the frost line in cold climates. Ensure adequate pitch to prevent standing water from freezing.
- Fix: Re-excavate and adjust pipe depth or pitch.
When to hire a pro
Consider hiring a professional for:
- Complex Systems: If you have multiple downspouts, a sloped yard, or need to connect to a dry well or French drain.
- Permit Requirements: Some areas require permits for underground drainage work.
- Heavy Excavation: If the job involves significant digging or working around existing utility lines.
- Guaranteed Results: Professionals offer expertise, specialized equipment, and often warranties on their work.