#5-Downspout Runoff

Popup #5

Downspout Runoff

Downspouts pour an average of 250 gallons per inch of roof runoff near the foundation, often into clogged drain lines. Maintenance is key.

Downspout Drainage Systems

Managing Roof Runoff

Gutter systems collect hundreds of gallons of roof water per inch of rain. The average downspout discharges about 200 gallons per inch of rain and can basically fill up about 4 rain barrels at every corner of a home in a 10 minute downpour. Runoff from the roof/ downspouts is/ are the number one cause of foundation problems including structural problems/ cracking/ undermining, flooding, mold and water intrusion. Excess water around the property also attracts pests such as moles, voles, mosquitoes and giant cockroaches, otherwise known as water bugs.

 Gutters are generally recommended to collect rainwater runoff from the roof. The gutter water goes down the downspouts and dumps around the foundation unless a proper downspout drainage system is installed. 

Many builders and landscapers bury corrugated pipe to carry this water away. This is a temporary solution since corrugated pipe should be used for above ground temporary use only until a proper PVC system can be installed. 

Why is PVC pipe so much better than corrugated?

• A PVC drainage system basically does not depreciate. It will still work as good as new a lifetime later if properly maintained.
• PVC pipe is smooth with a larger inner diameter so it can handle twice the volume of water compared to corrugated pipe which has ridges that cause friction. There is double walled corrugated pipe but the inner diameter is considerably smaller. 
• Corrugated pipe is connected by loose, leaky fittings. These fittings not only allow water to leak out which can undermine structures. 
• Ridges in corrugated pipe hold water and attract roots which get in through the loose leaky fittings. Once roots get in, leaves and other debris get caught on them and cause the pipe to clog.
• Corrugated pipe holds water in the ridges that attracts mosquitoes and encourages mosquito breeding. 
• Corrugated pipes are easily crushed. Weed eaters can easily cut through them, leaving holes where they extend from the ground to the downspouts which lets downspout water leak out and cause damage to the foundation.
• The ridges in corrugated pipe can also cause sticks and debris to get lodged in the pipe which causes leaves to back up behind the caught debris filling the pipe solid over time. PVC pipe allows debris to slide right through and out the open end.
• If there ever is a problem with PVC pipe, rotary plumbing cleaning tools can be used to clean them out, whereas these tools can basically grind up corrugated pipe.
• The ABS plastic that black corrugated pipe is made of does not hold up well to sunlight and the corrugated pipe that extends up to downspouts out of the ground and tends to crack over time which causes water to flow out and can damage the foundation. 

A proper drainage system is installed correctly using the right materials the first time. It's a one-time job that once done properly should never need to be redone.

PVC Drainage System Maintenance: 

PVC drainage systems require very little maintenance. We typically run water in one end and make sure it comes out the other. The biggest problem we see is that water that trickles out the end of these pipes will cause plant growth. Of course if a tree grows up at the end of the pipe, it will block the end and cause the pipe to back up eventually. We have also seen homeowners or landscapers dump debris such as lawn clippings and cover up the end of the pipes which can over time cause them to back up. That's why we recommend testing basic downspout drainage systems at least once every 2 years.

Gutter System Alternatives, Ground Guttering:

We specialize in ground guttering systems and have our own product designed specifically for this purpose. 

Some homes are built without gutter systems. It is still critical to get this roof water carried away from the foundation. Ground guttering systems in the form of linear drains along the drip line of the eaves are an alternative to standard gutter systems. In wooded areas where gutters will likely be easily clogged by leaves, this can be a great alternative. Also, it can be difficult to install gutters on metal buildings. They typically need to use straps that screw into the metal roof which may not be ideal.