Our current climate of extremes can bring us periods of monsoonal downpours and weeks of excruciating dryness. Each presents its own challenges: How to keep vegetation alive with minimal moisture and what to do with all that water when it does fall from the sky. Let’s talk about water and a great way to treat downspouts.
Every spring as normal rains fall, we receive numerous calls about “drainage problems”, many linked to downspouts. With all new construction, downspouts pose a design dilemma to solve. Almost every home has them. Often they are ignored or forgotten. How should downspouts (and gutters) be treated?
First – They should be kept clean and checked regularly for blockage.
Gutter guards of some kind – there are many different kinds commercially available – are a good start, especially for homes in wooded areas with lots of debris (leaves, small twigs, fruit and seeds, etc.) falling and potentially clogging gutters and downspouts.
Goals
There are many options for how to deal with the water that flows out of a downspout. Goals are to:
- Direct water to a place where its flow or percolation into the ground does not cause a problem.
- Minimize the amount of water that flows off the property. As the percentage of impermeable surfaces (covered by buildings, pavement, etc.) increases, rainfall landing on these surfaces is looking for someplace to go. Allow as much water as possible to percolate into the ground within the property, and not flow off the property, contributing to water issues elsewhere. In dense urban environments, this is particularly challenging.
Problems
The simplest option is to have the water just flow out onto a plastic or concrete splash guard and onto the ground where it simply soaks in, or directly onto pavement. Potential problems are:
- The water is released in close proximity to a basement wall and because of inappropriate grading, wall in poor condition, or other reasons, it ends up contributing to basement water problems. Solution: If possible, improve grading or take other steps to direct water from basement wall.
- The water is released at the base of a plant that suffers from the excessive water it receives during periods of heavy rainfall. Solution: If possible, direct water away from the vulnerable plant.
- The force of the released water is strong enough to cause erosion. Solution: Add a grouping of stones at the end of the splash guard to deflect and slow water as it flows onto the ground.
- Water flowing onto pavement in winter an freeze and create icy spot. Solution: None.
If water needs to be taken further away from the bottom of the downspout to be released safely (away from basement, vulnerable plant, etc.), a downspout extension or pipe of some sort can be attached and placed atop the ground. Problem: Unless the extension can be hidden in some way it doesn’t look very good.
Underground Flow
A visually better solution is to connect the downspout to pipes running underground to a suitable release point. The water can be released in several ways:
- If running to a relatively hidden, sloped, non-lawn location, the pipe can naturally expose itself, the water simply flowing out onto the ground. Stones may want to be placed off the end of the pipe to limit erosion. A metal “animal guard’ can be connected to the end of the pipe to prevent critters from inhabiting the pipe.
- the pipe can run to a “French Drain”, a pit of course (golf ball size is good) gravel. The pipe connects to a “T” at the pit. One arm allows water to drop down into the gravel and percolate into the ground. When the gravel pit becomes saturated, the water level rises up into the arm of the “T” which extends to ground level where a grate permits water to bubble out onto the ground and flow away as the grade dictates.
- Often, pipes from several downspouts will be combined. In this case a more substantial structure might want to be installed, capable of handling a greater capacity of water. A product we use is call a “Flo-Well”. It is essentially a “barrel” with holes in its sides and an open bottom. it is buried surrounded by gravel. Water from downspouts is fed to it and held in the barrel while it percolates through the gravel and into the ground. Like a “French Drain”, when it is filled to capacity, excess water will rise to the surface where it is released through a grate opening.
Potential problems:
Any underground pipe can be vulnerable to becoming clogged with debris. It must be checked and possibly cleaned periodically. If a serious blockage occurs, a “plumber’s snake” or other pipe clearing device may be necessary. Because of this possibility, the use of smooth white PVC pipe is recommended as opposed to black corrugated pipe which is not compatible to and can be damaged by this operation.
Likewise, the French Drain can become full of debris and will periodically need to be cleared or even reinstalled. Simple cleaning can be done by removing the grate and reaching a hand in and pulling out the nastiness that has collected. It’s not necessarily a pleasant task and one for hands on the smallish side.
An alternative that helps keep some debris out of the underground pipe is to have the downspout not connect directly to a pipe. It would instead empty onto and through the grate of a square catch basin – a box (perhaps 12”x12”) that the water would drop into before exiting through a pipe in its side to be released in any of the manners described above. This method allows a double “filter” of the water before it flows through the pipe, thus limiting debris and the potential for clogging. First, larger debris is caught by the grate atop the catch basin. Second, some debris that does fall into the catch basin will settle to the bottom without flowing into the pipe. The catch basin, with its relatively large top, is easily accessed and cleaned.
Environmental Sensitivity
While any option that allows water to soak into the ground on your property is environmentally responsible, several options take your level of sensitivity even further.
- Collecting downspout water in a rain barrel allows you to use the water later in your garden. There are countless styles, colors and capacities available for home use.
- Rain water harvesting can be taken even further though underground storage and be as complex of a system as budget and technology capabilities allow. Storage tanks can collect all downspout and/or surface drainage. The appropriate pump(s) can allow the collected water to be used by an irrigation system or general garden use.
- Rain gardens are an increasingly popular and sensible way to accommodate water on a property, both from downspouts and off pavement. A depressed area is created where water is sent with the purpose of allowing it to collect, sit (up to a certain depth), and soak into the ground. The area should be planted with vegetation appropriate for and tolerant of periods of saturation.Many useful books and articles are available that expand on these very brief descriptions.
Other hints/mistakes to avoid:
- If connecting a rectangular downspout to an underground pipe – use a downspout adapter. One end is rectangular and matches the shape of the downspout and the other end is round (typically 4″ dia.) and meant to connect to pipe. Don’t just place a round pipe around the end of a rectangular downspout. A round pipe connecting to a round downspout is fine.
- If black corrugated pipe is being used to carry downspout water (not my preference), it should run straight down into the ground and connect to a 90 degree coupler, after which it would run underground. Do not just use the corrugated pipe’s bending capability to create a curve. It doesn’t look good or professional.
- To assist with future cleaning of an underground pipe, install a “clean-out” opening just below the downspout adapter but just above ground level. This would be created by using a “Y” connector. The side “leg” of the Y can be capped or covered with a grate. It will provide easy access into the pipe should it be necessary for a hose or other cleaning item. Otherwise the downspout adapter and connecting pipe will be (should be) snugly connected to the downspout and typically harder to get access to without damaging or dislodging the downspout. additionally, “clean-outs” may be desired along the run of an underground pipe for additional access. This would consist of a “T” in the pipe with an access pipe running to ground level and capped.
- Any section of underground downspout line that passes beneath paving (driveway, walk, patio, steps, etc.) should be Schedule 40 PVC pipe and not a thinner drain pipe or black corrugated pipe. This thicker pipe has the strength necessary to not be compressed or damaged by the pressure of the wight above it.
- Water flows downhill. All underground pipes should be installed to allow this to happen.
Downspouts present challenges and opportunities. However they are addressed or embraced, by whichever of the options discussed, the end result must be functional and look good.
David Gorden, ASLA