Great Lakes Green Pages

Today, I am researching rainwater harvesting systems. There are many products available on the market these days, but I am starting with the few that I remember from Greenbuild. What is Rainwater harvesting? It is the process of capturing and reusing rainwater that runs off of a building’s roof. It can be used for irrigation and more. Depending on many factors, like roof compsition and local regulations, it can be used for laundry and showering. We plan to capture the roof runoff and reuse it for irrigation, and possibly to flush toilets. In order for this to work, we need to accurately plan on capturing a month’s worth of rainwater. Some people may be surprised to learn that Cleveland has an annual rainfall that is on par with Seattle. That means a significant amount of rainwater retention capability. We expect to need 6-8 thousand gallons of capacity.

But why capture rainwater in the first place? Managing the run off from a building site can have a huge impact on the local water shed. First off, letting rainwater run into the gutter and using fresh potable (drinkable) water to water landscaping makes no sense whatsoever. Secondly, rain runoff picks up dirt and oils, then enters the sewer and has to be cleaned up before delivering to the municipal supply or watershed. In a city like Cleveland, whose infrastructure is in dire need of updating, managing our own stormwater can help to reduce sewer overflows. We plan to use captured rainwater for irrigation. Furthermore, we plan to remove as much concrete from the site as possible. Concrete caused rainwater to run off site and into the sewer. We plan on utilizing permeable pavers on site. Pavers that allow water to pass through them, allows water to filter through the ground and re-enter the water shed naturally, filtered by the earth itself. Once we work out the logistics, we may need to add a bio swale in order to treat additional run off.

Rainwater Harvesting

Here is an image by Construction Resources in the UK that illustrates how the idea works.

We are looking at a variety of companies. They all have advantages and disadvantages, but all work on the basic principal of the old fashioned rain barrel. A tank of some sort is connected to the downspouts on the roof and rainwater is collected and stored in it. My favorite design is the Rainwater HOG. The reason that I like this system is the design of the barrels. They are about 6 feet tall, less than 2 feet wide and only 9 1/2 inches deep. While these 50 gallon tanks may not come anywhere near being large enough for any one structure, the advantage is that they are modular and the system is expandable. They fit together to increase capacity to the necessary size. They can be used upright or horizontally. That means they can stand up along a fence line or retaining wall, or lay under a deck. These great tanks are reusable and recyclable at the end of their life, and are made of food grade plastic. Another system that is interesting is the Rainwater Pillow. It functions like a giant water bed mattress. It is cool in that it can be designed specifically for your situation. This is ideal for homes with a partial basement area or large deck area that is unused. It can even be designed with Cradle to Cradle Specifications. The final type of tank is a rigid solid tank. Bushman makes a variety of sizes in polyethylene. Containment Solutions make a fiberglass selection. These two companies provide similar solutions with one major difference: Bushman is made for smaller applications and meant to be used above ground. Containment Solutions seems to be for larger applications and mainly utilized underground. Our particular project is difficult as it mainly falls between the two. While it is a commercial site, it isn’t a huge site. If we chose a company like Bushman, we would need their largest size in multiple units. These would take up a lot of room on site, unless utilized in the basement. Here they would need to be much smaller, however, in order to install them. While an underground system, like those of Containment Solutions would be easier to implement, it would require immense digging to install. This makes sense in a new construction project, but much less in a retrofit situation.

The last things to consider are usage, access, and peripherals. What you plan to use the water for makes an important impact on the system selection and add-ons. We plan to use it for mainly rainwater collection and irrigation. That means a simple filter could be used at collection to keep out particulates. This also means we would need little access to the tanks themselves as there will be little clean out needed. We intend to add showers to the plan. Shower water can also be collected, as long as biodegradable soaps are used. This however, would mean finer screening and filtration to keep out larger particulate matter. The trade off is a reuse of waste water. In any case, we will likely need pumps to use the water. Outdoor tanks, above ground, would mean that pumps could be avoided for some of the water use, utilizing simple gravity to use induce pressure. Underground tanks would mean pumps are a necessity.

We may use a combination of brands. Additionally, after a year or so of use, we plan to try installing a system in our own home. This project should give us some insight into what will work best for our house. As always, any feedback on rainwater collection systems would be greatly appreciated!