Downspout Disconnection: Redirect Roof Runoff from Your Foundation

Downspout disconnection is one of the simplest and most effective stormwater management practices. By redirecting roof runoff away from foundations and storm drains, you protect your home while reducing flooding and pollution downstream.

Why Disconnect Downspouts?

The Problem with Connected Downspouts

Many homes have downspouts that:

• Dump water directly at the foundation
• Connect to buried pipes leading to storm drains
• Discharge onto impervious surfaces that drain to streets

This causes several problems:

• Foundation damage from water pooling against walls
• Combined sewer overflows in older cities
• Stream erosion from concentrated runoff
• Pollution carrying directly to waterways

Benefits of Disconnection

For Your Property:

• Protects foundation from water damage
• Reduces basement moisture/flooding
• Irrigates landscaping naturally
• Decreases ice buildup in winter

For Your Community:

• Reduces storm drain flooding
• Decreases combined sewer overflows
• Filters pollutants through soil
• Recharges groundwater

How Much Water Are We Talking About?

Roof runoff volume is substantial:

Where:

• V = Volume in gallons
• P = Precipitation in inches
• A = Roof area in square feet

Example: 1,500 sq ft roof section, 1-inch rain:

That’s nearly 1,000 gallons from just one section of roof in a moderate rain!

Disconnection Methods

Method 1: Extension to Pervious Area

The Simplest Approach:

1. Cut or disconnect the downspout above grade
2. Attach an extension (rigid or flexible)
3. Direct water to lawn, garden, or mulched area
4. Ensure water flows away from foundation

Extensions Options:

• Corrugated flexible pipe - Inexpensive, easy to route
• Rigid PVC pipe - Durable, cleaner appearance
• Above-ground plastic/metal - Easy to adjust seasonally
• Decorative chains - Rain chains for aesthetic appeal

Minimum Extension Length: 6 feet from foundation (10 feet preferred)

Method 2: Buried Pipe to Daylight

More Permanent Solution:

1. Dig trench from downspout to discharge area
2. Install 4” solid pipe with proper slope (1/4” per foot minimum)
3. Connect downspout adapter at house
4. Terminate with pop-up emitter or outlet

Advantages:

• Hidden from view
• No seasonal adjustment needed
• Can handle higher flows

Considerations:

• More expensive to install
• Requires trenching
• Must avoid utilities
• Freeze potential in cold climates

Method 3: Rain Garden or Infiltration

Best for Stormwater Management:

1. Create depressed garden area 10+ feet from house
2. Direct downspout extension to garden
3. Garden plants filter and infiltrate water
4. Overflow outlet handles large storms

Learn more about rain gardens →

Method 4: Rain Barrel Connection

Capture for Later Use:

1. Install rain barrel(s) at downspout
2. Barrel has overflow that must be directed away
3. Use collected water for irrigation
4. Empty before rain events during wet season

Installation Steps: Basic Extension

Tools and Materials

Materials:

• Downspout extension (corrugated or rigid)
• Elbow fittings (if needed)
• Sheet metal screws or clamps
• Splash block (optional)

Tools:

• Hacksaw or tin snips
• Drill/driver
• Level
• Tape measure

Step-by-Step

Step 1: Assess Current Setup

• Where does downspout currently discharge?
• Is it connected to underground pipe?
• What’s the best discharge location?

Step 2: Disconnect (if needed)

• If connected to underground, cut pipe at grade
• Cap underground pipe if not removing
• Some cities require professional disconnection

Step 3: Install Elbow

• Add elbow to direct water horizontally
• Secure with screws or clamps
• Ensure water-tight connection

Step 4: Attach Extension

• Connect extension to elbow
• Route toward discharge area
• Maintain slope for flow
• Secure any above-ground sections

Step 5: Prepare Discharge Area

• Add splash block to prevent erosion
• Consider small gravel pad
• Ensure positive drainage away from structures
• Plant grass or groundcover to stabilize

Step 6: Test

• Run hose into gutter
• Verify flow through system
• Check for leaks at connections
• Confirm water disperses properly

Best Practices

Discharge Location Requirements

Distance from Structures:

• Minimum 6 feet from your foundation
• Minimum 6 feet from neighboring foundations
• 10+ feet preferred for problem areas

Ground Conditions:

• Slope away from all structures
• Pervious surface (lawn, garden, gravel)
• Not toward sidewalk or street (defeats purpose)
• Not toward neighboring properties

Soil Considerations:

• Well-drained soil is ideal
• Clay soil may need French drain or rain garden
• Avoid septic drain field areas

Avoiding Problems

Don’t Create New Issues:

• Verify drainage away from structure
• Consider neighbor’s property
• Check for basement windows in path
• Avoid eroding landscaping

Cold Climate Considerations:

• Disconnect flexible extensions in winter
• Use frost-resistant installations
• Consider ice dam potential
• Keep discharge away from walkways

Troubleshooting

Water Pooling at Discharge

Causes:

• Extension not long enough
• Negative grade toward house
• Clay soil not infiltrating

Solutions:

• Extend further (10+ feet)
• Regrade to slope away
• Install French drain or dry well
• Create rain garden

Erosion at Discharge

Causes:

• Concentrated flow on bare soil
• Steep slope at outlet
• High flow velocity

Solutions:

• Install splash block
• Add gravel energy dissipator
• Spread flow with perforated pipe
• Establish vegetation

Neighbor Complaints

Causes:

• Discharge crossing property line
• Creating wet conditions next door
• Erosion onto their property

Solutions:

• Redirect to stay on your property
• Install infiltration area
• Consider rain barrel or dry well
• Discuss and find mutual solution

Mosquito Concerns

Causes:

• Standing water in clogged extensions
• Pooling at discharge area
• Rain barrel without screen

Solutions:

• Maintain positive flow (no clogs)
• Ensure complete drainage
• Screen rain barrel openings
• Address pooling within 24-48 hours

Local Programs and Requirements

Check Local Regulations

Some areas have specific requirements:

• Mandatory disconnection - Some cities require it
• Prohibited discharge - Some limit where you can discharge
• Permit requirements - Major modifications may need permits
• Combined sewer areas - Often encouraged or required

Incentive Programs

Common program types:

• Rebates - Cash back for disconnection
• Fee credits - Reduced stormwater fees
• Free materials - Rain barrels, extensions provided
• Technical assistance - City staff help with design

How to Find Programs:

• Search “[Your City] downspout disconnection program”
• Contact local stormwater utility
• Check municipal water/sewer website
• Ask at local hardware stores

Cost Estimates

DIY Installation:

Professional Installation:

• Simple extension: $75-150
• Buried pipe system: $200-500
• Complete rain garden: $1,000-3,000

Summary

Downspout disconnection is an easy, effective way to:

1. Protect your foundation from water damage
2. Reduce flooding in streets and basements
3. Support natural infiltration and groundwater recharge
4. Save money on potential water damage repairs

The basic approach is simple:

• Redirect downspout away from foundation
• Extend at least 6-10 feet from house
• Discharge to pervious, well-drained area
• Ensure water flows away from structures

Check for local incentive programs that can offset costs or provide materials.

Related Guides and Calculators

• Residential Drainage Basics →
• French Drain Installation →
• Gutter Sizing Calculator →
• Green Infrastructure Basics →

References

1. Philadelphia Water Department. (2020). Downspout disconnection guide. City of Philadelphia.

2. Environmental Protection Agency. (2021). Managing wet weather with green infrastructure. EPA.

3. Portland Bureau of Environmental Services. (2020). Downspout disconnection program. City of Portland.

4. Low Impact Development Center. (2019). Residential downspout disconnection. LID Center.

5. University of New Hampshire Stormwater Center. (2017). Fact sheet: Downspout disconnection. UNH.