The western United States -- particularly California -- has been parched by extreme drought conditions for nearly four summers now. As a result, many state and local governments are beginning to restrict water usage to conserve resources. What can you do to limit your water consumption without dramatically changing your lifestyle? Read on to learn more about how your home's roof help you weather a drought by providing you with "grey water" to help flush toilets, water lawns, and wash cars.
What are grey water collection systems?
There are several types of grey water collection systems that can be relatively easily and inexpensively installed on your current roof. Most involve the installation of special gutters that travel to a central holding and condensing container. This container can help distill water from even slightly humid air -- so rather than waiting for the (very) occasional rainfall, your system can collect grey water on a daily basis during the cooler time just before dawn.
After installing the holding container, you'll need to hook this container up to either an outdoor hose or an indoor plumbing system. If you plan to use this water only to water your lawn or garden or to wash your vehicle, you may be able to finish this step simply by screwing an ordinary garden hose into the holding tank.
However, if you'd like to use your grey water to flush toilets, or are interested in distilling this water and using it for bathing or washing clothes, you'll need to engage the services of a roofing contractor and plumber to help route your system to the correct pipes.
What roofing material is best suited for the installation of a water collection system?
Although you might be reluctant to install a water collection system on a roof with asphalt shingles -- thinking a smooth metal roof or sturdy slate-shingled roof would be a "cleaner" choice -- an asphalt-shingled roof is actually your best and healthiest option.
Over time and without regular cleaning, smooth-surfaced roofs build up invisible layers of polycyclic aromatic hydrocarbons (PAH). This toxic film is created when air molecules containing smoke, car exhaust, gasoline fumes, and other foul-smelling substances pass along your roof, depositing the heavier PAH molecules on their way.
Rough-surfaced roofs seem to be relatively resistant to the deposit of PAH molecules, and are better at retaining the molecules that are deposited (so that water passing over them does not become contaminated).
Another risk for smooth roofs -- particularly in agricultural or heavily-populated areas -- is the presence of fecal bacteria. If livestock is farmed nearby, the air above your roof is likely filled with microscopic fecal particles. Although these bacteria are generally harmless if encountered individually, the layers that can build up on a smooth roof may end up in your water supply if you aren't careful. Although you're not consuming this water, you'll still want to remove as much PAH and fecal bacteria as possible to prevent damage to your appliances, lawns, vehicles, and whatever else you use this grey water to clean or grow.
Are there modifications you can make to your current roof?
If you have a smooth roof and don't want to replace it to harvest water, there are a few steps you can take to minimize the effects of PAH and fecal bacteria in your roof runoff.
First, you may be able to keep PAH particles on your roof (not in your water) by placing a thin netting material or other shield between the air and your roof. By giving PAH particles and other bacteria a rough surface to which they can cling (even if it's only a loosely-woven net), you can avoid the build-up of a smooth film that immediately yields to the water running above it.
You may also want to invest in a distillation or purification system that will help clean the water after it's been collected. If you have measurable levels of PAH or bacteria in your water, this is likely your safest way to ensure that the grey water you're using is relatively clean. For more information, contact a local residential roofing expert.