Disconnecting Your Downspout And Diverting Stormwater

Downspouts direct rainwater (also called stormwater) from rooftops to driveways, sidewalks, or underground pipes that lead to sanitary sewer systems or storm sewer systems. When directed to driveways and sidewalks, the rainwater picks up various pollutants as it travels over these surfaces. Common pollutants found in rainwater runoff include: motor oil, sediment, pesticides, fertilizers, grease, trash, and animal waste from pets and wildlife. This runoff is typically directed from the driveway/sidewalk to the road where it enters a storm sewer system, which may be a network of catch basins and pipes or roadside ditches that lead to local streams, rivers, lakes, wetlands, or estuaries. This water travels quickly and at high volumes untreated to these waterbodies. Downspouts may also be directly connected to the sanitary sewer system or storm sewer system through underground pipes.  Downspouts that connect directly to the sanitary sewer system increase the likelihood of “sanitary sewer overflows.”  Sanitary sewer overflows occur when the sewage treatment plant cannot treat the amount of incoming rainwater and sewage, resulting in raw sewage discharges to local waterbodies.

To reduce polluted rainwater runoff and/or decrease the chance of sanitary sewer overflows, you can disconnect your downspout and divert the rainwater to a garden or vegetated area on your property. In cases in which downspouts are already disconnected, you can use splash blocks or gravel-filled trenches to disperse the rainwater. These methods prevent rainwater from leaving your property by diverting it away from the foundation and directing it toward a vegetated area (lawn or garden).

What does it mean to disconnect a downspout?

Downspout disconnection means that you are disconnecting the connection between your downspout and the storm sewer system or sanitary sewer system and allowing rainwater to infiltrate on your property. Downspouts are typically connected in one of three ways. In some homes, the downspouts discharge to a driveway or sidewalk, which drains the rainwater into the street and into the storm sewer system via roadside ditches or storm drains. In other homes the downspouts are directed through a pipe underground to the sanitary sewer system or storm sewer system. See Figures 1, 2, and 3 for an illustration of the ways in which a downspout can be connected. This drainage path directs water off your property and into a storm sewer system or sanitary sewer system, which has negative affects on local waterbodies. You can take control of where your rainwater goes by disconnecting your downspout to allow the water to drain into your garden or lawn.


Figure 1: Downspout connected to sewer intake pipe (standpipe).

(Image courtesy of Mid American Regional Council (MARC) http://www.marc.org/Environment/water/downspout.htm)

What are the benefits?

There are many benefits to disconnecting your downspout. If your downspout is connected to the sanitary sewer system, the simple act of disconnecting your downspout can divert hundreds of gallons of water from the sanitary sewer system each year. This diversion of rainwater benefits the environment, the public, and homeowners as it decreases the amount of raw sewage discharged into local waterbodies and helps to prevent sewage backup and basement flooding. If your downspout is connected to the storm sewer system, disconnection will reduce the amount of polluted water that flows into the storm sewer system.  Thereby reducing the amount of polluted water reaching local waterbodies and erosion caused by high volumes of water that flow from storm drain outfall pipes.

Disconnecting a downspout that directs rainwater to a driveway and sidewalk will help reduce the amount of polluted rainwater (also referred to as stormwater) that enters local waterbodies. Rainwater that flows over driveways and sidewalks picks up various pollutants such as motor oil, pesticides, fertilizers, pet waste, and sediment. This polluted rainwater negatively affects water quality and can harm fish, wildlife, and plants that depend on healthy streams, rivers, lakes, or estuaries.

Infiltrating water on your property is also beneficial for groundwater. Many communities depend on groundwater for their drinking water and the process of infiltration helps clean the water and recharge groundwater supplies. Directing roof rainwater to your lawn or garden will also save you money. Using rainwater to water your lawn or garden will reduce or eliminate the need for additional watering, thereby reducing your water utility bill.

In essence, disconnecting downspouts can create multiple benefits for the environment and for yourself by keeping the water on your property and decreasing the amount of polluted water that enters into local bodies of water.

How do I know if I should disconnect mine?

If you want to know if you should disconnect your downspout, first determine where your downspout drains to (a sanitary sewer system, storm sewer system, drywell, gravel-filled trench, splash block, driveway, or sidewalk). If your downspout drains into a gravel-filled trench, splash block, or drywell; it is not necessary to disconnect your downspout. If you think your downspout is connected to the sanitary sewer system or storm sewer system, call your local sewer system authority or public works department to find out for sure. If it is, inquire if there are any regulations against disconnecting the downspout or if a professional is required to do the work. 

How do I disconnect my downspout?

The task of disconnecting your own downspout is relatively simple, but it must be well-planned out. The following are materials and tools you need to have before starting:

  • Hacksaw
  • Drill
  • Pair of needle-nose pliers or crimpers
  • Tape measure
  • Screw driver or nut driver
  • Sheet metal screws
  • Downspout elbow and downspout extension
  • Rubber cap and hose clamp or wing-nut test plug (if downspout is connected to sewer standpipe.)
  • Bracket or Strap (if downspout is not secured to the building structure)
  • Crimpers or pliers

There are three steps to disconnecting your downspout (Acquired from City of Portland Environmental Service):

1)       Make a site plan. Sketch your site plan and your roof plan. You can also print an aerial view of your property from Google Earth, MapQuest or other mapping program. Mark the locations of the downspouts and roof line and estimate the square footage of your roof area. Also map out or mark areas in your yard that are down slope of where you might disconnect downspouts.

Fig4_Ex_SitePlanFigure 4: Example Site Plan

 2)       Design your disconnection. On your site plan or aerial image, mark the downspouts that are to be disconnected and the direction of flow. Mark the location of any septic systems or drinking water wells. Keep in mind that water should be directed away from septic systems and drinking water wells, as well as any structures. Note where you might move downspouts, remove walkways, pitch gutters, and/or add extensions or elbows to get around obstructions (plants, trees, porches, sidewalks). 

SitePlan_DSFigure 5: Site plan with downpouts marked and direction of flow illustrated. 

One design consideration is to replace impervious surfaces like concrete with materials like permeable pavers or gravel. This allows rainwater to infiltrate into the ground.

DS_Ext_PermeableFigure 6: Downspout extension draining to permeable pavers.

Picture from Montgomery County Maryland DEP


Another option is to extend downspouts underneath a deck or raised patio to a landscaped area.


Figure 7: Downspout extended under deck to landscaped area.


3)       Disconnect your downspout. Measure your downspout from the top of the standpipe and mark it at 9 inches above the standpipe. Depending on the length of your extension, you may need to cut it higher. (See Figure 8). Cut the downspout with a hacksaw at the mark, and remove the piece.

Fig8_Cut_DSFigure 8: Illustration showing how to cut the downspout.

C. Cap or plug the standpipe with either a wing-nut test plug or rubber cap with hose clamp. Do not use concrete to seal your standpipe.

Fig9_PlugsFigure 9: Example of a plug with wing nut and a cap with hose clamp. 

D. Attach the elbow externally over the downspout, not inside the downspout or it will leak. If the elbow does not fit, use crimpers or pliers to crimp the end of the cut downspout so it can slide inside the elbow.

Fig10_attach_elbowFigure 10: Illustration of how to attach an elbow over the downspout.

E. Measure and cut your downspout extension to the desired length. Connect the extension to the elbow by slipping it over the end of the elbow. If your house is set on a crawl space or concrete slabs, your extension need only be 2 feet long. If your house has a basement, the extension must be at least 6 feet long.

Fig11_extensionFigure 11: Illustration how to attach a downspout extension to an elbow.

F. Secure the elbow and extension with sheet metal screws at each point where the downspout, elbow, and extension connect (pre-drilling the holes will help). If desired, use a splash block at the end of the extension to prevent soil erosion. Avoid draining water onto impermeable plastic weed block or cloth.

Fig12_secure_elbowFigure 12: Illustration of how to secure the elbow and extension.

What types of materials should I use or avoid? 

Material that you use for your downspout elbow and extension should be a durable gutter-grade materials, such as steel, copper, aluminum, vinyl, or plastic. Also, downspout extensions and elbows come in multiple standard shapes, sizes, and colors. A good option is black ABS SCH 40 plastic, which can be found in most hardware stores and home centers. If you are looking for flexibility, a hinged downspout elbows is another good alternative because it allows you to flip up the extension against the house during dry weather or lawn mowing. 

In terms of materials that you should not use, try to avoid corrugated black plastic, roll-out hose, PVC pipe, dryer hose, swivel, and open-trough materials because they have limited durability.

How do I maintain my new system?

When you disconnect your downspout, you may need to do occasional maintenance procedures to your gutters, downspouts, and landscape.

For gutters, make sure that you clean them and caulk leaks and holes at least twice a year. Also, make sure that the gutters are pitched to direct water to downspouts and that the roof flashing directs water into gutters. Look for low spots or sagging areas along the gutter line and repair it with spikes or new hangers.

As for downspouts, remember to check and clear elbows to prevent clogging. Make sure each elbow or section of the downspout funnels into the one below. All parts should be securely fastened together with sheet metal screws.


What else should I know about disconnecting my downspout?

  • The slope of the ground should allow water to flow away from all structures, but you should not disconnect a downspout on slopes over 10 percent.
  • There must be enough landscaped area for the rain to safely soak into the ground. Specifically, the ground area must be at least 10 percent of the roof area. For example, if your roof is 500 square feet, you should have at least 50 square feet of landscape.
  • The end of the downspout extension must be within your property line by at least 5 feet and at least 3 feet from a public sidewalk.
  • Try to avoid safety hazards by not extending downspouts across walkways, patios, or driveways, or in front of gates.
  • Keep downspout drainage away from a septic system, drain field, drinking water well or underground oil tank. 
  • Do not disconnect downspouts within 10 feet of a retaining wall.
  • You could incorporate stormwater management practices into your downspout disconnection. Consider installing a rain barrel or rain garden to capture and infiltrate rain water.

Once you have disconnected your downspout, you may consider adding splash blocks or gravel-filled trenches to the end of the downspout extension to prevent erosion and disperse the rainwater.


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