One often overlooked but important part of home maintenance is drainage. We spend so much time, effort and money in finding ways to get water on to our property, it comes as no surprise that we don’t always consider it’s just as important to be able to divert water off of our property. The reasons we might want to do this are to protect the foundation of the home, to protect the roof from water damage, to prevent flooding basements or even to ensure the health of our lawns and other landscaping plants. Standing, stagnant water can also proliferate water and air borne diseases. Finally, drainage can also be used for irrigation.
To prevent these problems, there are several different types of drainage that can be employed to divert water away from areas it accumulates. Gutter and downspout diverts water away from the roof, surface and sub-surface drainage diverts it from the ground, usually depressed locations where water can pond, and slope drainage which is simply pipes installed on a downward slope. There are other types of drainage, and other terms for the types mentioned above, but these are the ones most residential drainage projects will consider.
These methods of drainage share similar characteristics; for example, a gutter and downspout is essentially a slope that leads into a steeper slope. Our guide will focus on area drains, a form of surface drainage that uses catch basins and a piping network to move water that would otherwise pool on the surface. This water may come from rain, gutter and downspout, or even sprinkler runoff. The system consists of one or more catch basins, a piping network that moves the water away from the area it pools in; common locations to move the water include storm drains, the street gutter, an alley or a location with plants that need to be irrigated. Note, catch basins are not always necessarily used; locations without much debris can simply use a grate attached to a drainage pipe. It is common for the end of the drainage system to end in a drainage emitter, a type of pop-up that only emits water when the pressure from the full pipe becomes sufficient to push the spring cap open. Below we will cover the components of this type of drainage system.
The is typically installed at grade or slightly below grade. It should be installed at the low point where water tends to pool, also known as “ponding.” The slitted grate not only helps prevent debris from entering, but also people and animals. The catch basin will have one or more outlets where pipe is connected to route the water away from where the water is ponding. The pipes leading away from the basin should travel downward, about 24” per 100’, that is approximately ¼” per 1’.
Catch basins come in several sizes and shapes;
square basins are frequently used with concrete and pavement, round basins see the most use in landscape applications. The basins have a sump at the bottom to collect debris that gets through the grate to prevent it from getting in the pipe and potentially clogging the drainage system. This sump area must be cleaned out periodically and after heavy storms; most catch basins will have perforated holes at the bottom to drain water that gets into the sump. If the area has mulch, leaves, sand, silt or grass clippings, a catch basin with a sump should be used.
This link goes to our catch basins: Catch Basins
Drain grates are attached either directly to drainage pipe or to the catch basin. They are slotted to allow water to pass through but prevent larger debris, and most importantly, animals and people from falling into the basin or drain pipe. Grates come in a wide variety of shapes and sizes. These shapes and sizes are not just aesthetic, there are practical reasons for the differences between them. Flat grates are most often used in concrete areas and turf areas. The flat at or just below grade shape allows landscape maintenance equipment (lawn mower, etc) to pass over without harm. Atrium grates work best in planter beds and other locations where things like mulch and leaves might otherwise easily clog a flat, ground level grate. Atrium grates also have larger open surface areas that can handle larger volumes of water and runoff.
Grates come in a couple different colors; the common approach is to match the color of the grate as closely as possible to its surrounding environs, thus we see green grates used in lawns, brown grates used in mulched beds, and gray grates with concrete. One word of caution: as an atrium grate is above grade, if it blends in too well with the surrounding landscape it could become a trip hazard, particularly as it gets darker.
Just as seen in irrigation, different sizes of pipe and grate can handle different levels of flow. At the end of this article there will be a link to a design guide that will walk you through calculating how much flow is to be expected from your drainage area; once this is done the chart below can be referenced to locate an adequate grate.
This link goes to a listing of our drainage grates: Drainage Grates
Not all grates are compatible with catch basins. The smaller grates will attach directly to 2”, 3" or 4” pipe. Larger grate sizes are compatible with catch basins. Note, in drainage systems that do not use a catch basin, debris could become a concern; drainage with no catch basin often makes a good solution when the location to be drained does not have a high risk of debris.
Though we do not currently carry any drainage pipe, no introduction to drainage would be complete without its mention and explanation. There are three main types of pipe used in drainage systems: Corrugated, Sewer and Drain Pipe, and Triple Wall Pipe. Each has advantages and disadvantages.
Corrugated pipe tends to cost less, in both up front and installation costs. Corrugated pipe has a lower cost per foot (in most cases) than the other types. It is flexible enough that fewer fittings, elbows in particular, will be needed to complete the designed installation. Its flexibility allows for lower shipping costs as it can be shipped in a smaller container. Long term costs don’t fare as well in many situations, however. In the event of a clog, corrugated pipe cannot be drain snaked, meaning maintenance costs could go up if it’s installed in a location in which debris might get into the line.
Sewer and Drain Pipe is simply thin walled PVC pipe. The interior walls are smooth, allowing for a drain snake to be used for cleaning or clearing clogs, however it’s significantly more rigid than corrugated pipe and fittings will be needed for turns for most types of sewer and drain pipe. Due to its rigidness, it is better at handling elevation changes in the drainage area than corrugated pipe is. Corrugated pipe is flexible enough that it will match the shape of the landscape over which it is laid, meaning you can get a lot of small peaks and valleys that can interfere with the flow of water. This can be ameliorated by using sewer and drain pipe or digging a very even trench.
Triple Wall Pipe, as the name implies, is more durable than the above types. Like the above, it is a rigid pipe that can handle uneven terrain very well, better than the other two types, but is smooth walled to allow for the use of a snake in the event of a clog.
Like irrigation tubing and pipe, drainage pipe has a maximum amount of water that should go through it at one time. In the cart below are the recommended maximum flow rates for various sizes of drainage pipe.
The dilemma in drainage is not lost on most people. You install a catch basin and grate at a low point on a property to capture water that would otherwise pool, but to divert it away you somehow need to drop the elevation even further beneath the surface. Digging a sloped trench can of course accomplish this, but there will be situations in which you want to bury the basin even deeper to attach the drainage pipes. Riser basins are the answer to this problem. The riser basin sits on top of the catch basin and is compatible with the correct sized grate, essentially extending the basin and pipe network deeper below the surface.
Here is the link to our basin risers: Basin Risers
Pop-Up Drainage Emitters
Why send all the drained water down the storm drain, out of the alley or otherwise off the property when you can direct it to locations that do need water? Pop-up drainage emitters combine the best of drainage and irrigation. It takes water that is not in a desirable location and moves it to a location where it can be used to improve the quality of the property.
In most cases these are used in lieu of a drain grate or even an open drainage pipe and are still used at the curb or similar drainage location. Because the valve closes, it eliminates the risk of debris, insects or animals entering from the end of the drainage run. With that said, they can (and often are) used as emitters.
Drainage emitters like this one are essentially relief valves. It’s a normally closed valve that will pop-up once the pipes fill and enough pressure builds to operate the spring in the valve. When the pressure drops below that threshold, the emitter will close and cease emitting water. Using one as an emitter takes some planning, particularly in regards to knowing approximately how much water will be draining from it. See the drainage design guide linked at the end of this article for more information.
This link points to our Drainage Emitters: Pop-Up Drainage Emitters
Drainage System Maintenance
Maintenance on a drainage system is as important as it is in an irrigation system. Catch basins must be cleaned, pipes must be cleared and termination points examined. Fall is the typical time to do this. For an area drain system, this is as easy as prying up the grate and cleaning out the catch basin by hand. Tools such as a shop vac or hand cultivator can be used, but it is not necessary. Clean out exit pipes as far as possible of all foreign debris, your hand or a shop vac can be used for that as well. If your drainage system ends in a drainage emitter, you can pop it up to make sure there’s no debris crowding the exit point.
When flushing the drain pipes themselves, use a hose or multiple hoses to send a large volume of water through the pipes to push out any remaining debris. Flush until the water coming out of the end is clear and clean. At this point the system is ready for use and the grates can be reattached to the basins and termination points.
Preventative maintenance will go a long way towards ensuring a long life for your drainage system. Raking up leaves, washing away sediment, periodically checking the termination points for blockages and proactively cleaning the catch basin after every storm will see your drainage system continue to be effective and efficient.
Now that you have been introduced to drainage systems, it’s time to design your own. Tempo, the manufacturer of our drainage supplies has written an easy to follow, 10 step guide to design your own drainage system. It goes into more depth on some of the concepts touched on above and is worth a read even if you’re not ready to completely design a drainage system. The design guide can be found at this link: Tempo 10 Step Surface Drainage Design Guide.
Thank you for reading. If you have any questions, comments or feedback, please Contact Us. We read and reply to every message we receive and would love to assist with your questions and learn from your feedback.