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What is gray water, and can it solve the global water crisis?

Collecting and Recycling Water

Although your plants will love gray water, it's not safe for you to drink or use.
Although your plants will love gray water, it's not safe for you to drink or use.
Jonathan Wood/Getty Images

Collecting gray water doesn't require a specialized system. For example, you could easily use your old pet water to give your plants a drink before refreshing the animal's water bowl. The same goes for the old water in your fish tank. Fishbowl water also has the added benefit of nitrogen-based nutrients from fish waste.

If you look around your house, you'll find a number of different places where you can find and reuse water. A free-standing outdoor air-conditioning unit produces 10 to 15 gallons of condensation on a hot day, and all of this is wasted [source: Free Patents Online]. There are some condensate collection kits available in stores that can collect your A/C unit's condensation and send it to an irrigation system.


­You can also collect water from a window-mounted air conditioning unit. Simply place a bucket underneath the system to catch the condensation that drips from it. You can add a drip irrigation system to the bucket for low-maintenance plant watering. What's great about using A/C units as a source for reusable water is that they produce the most condensation during the hottest months, when watering bans are most prevalent.

Bath water is considered the best source for gray water, but collecting it using a bucket can be tedious and backbreaking. One British company figured out a way to collect bath water easily with the Ban Beater. This system uses a hose and suction to siphon the water into a cistern, which can be toted outside and used for localized watering.

Perhaps the easiest place to collect gray water, though, is from your clothes washer. Most models have a drain pipe exiting the back of the washer. Water can be easily removed from the drain to the sewer and placed into collection buckets. Just be sure, when collecting gray water with this method, that you have enough buckets and quick reflexes to catch all of the water exiting your washer during the drain cycle.

Professionally installed gray water collection systems feature extra plumbing that separates gray water from black water sources. These systems collect gray water, send it to a central filter and pump it out into an irrigation system. It's imperative these systems contain an emergency shut-off valve, in case of malfunction. They should also include a way to route your gray water into the sewer when you don't need it. These systems are much more expensive than doing it yourself, but are more convenient, too.

Whether you have a professional system or collect gray water your own way, it's important that any system you use have a filter -- it can be as simple as a nylon stocking or a window screen -- to remove debris like hair and grease from the water before you use it for irrigation. You should also pay attention to the amount of gray water you use for watering your plants. The University of Massachusetts suggests that you use a half gallon of gray water per square foot of well-drained garden soil per week [source: UMass].

So will gray water solve the global water crisis? Not by itself. But as awareness of its benefits grows, gray water could take a chunk out of the amount of fresh water people use. After all, watering plants constitutes 15 percent of the 400 gallons the average American household uses per day. If everyone in America used only gray water for their plants, it could save 6.6 billion gallons of water every day. Even better than that, when you reuse water, you save electricity, since it takes power to pump water to your house. This electricity is often generated at coal-fire power plants, so reusing water can actually help clear the air, too.

For more information on water, recycling and related topics, visit the next page.

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More Great Links


  • "What is Gray Water?" Arizona Department of Environmental Quality.
  • "100 Water Saving Tips." Water Use It Wisely.
  • "Tips for Reusing Graywater."
  • "Filter Assembly for Gravity-Assisted Air Conditioner Discharge Water Saver Systems." Free Patents Online. April 12, 2005.
  • "How Much Graywater Do I Produce?" Innovative Water Solutions.
  • "Conserving Water At Home." University of Georgia.
  • "Outdoor Water Use in the United States." U.S. Environmental Protection Agency. October 26, 2007.
  • "Projections of the Number of Households and Families in the United States: 1995 to 2010." U.S. Census Bureau. April 1996.
  • "Reused Water, Plumbing Tips Help Trim Consumption." WRAL. August 24, 2007.
  • Barker, Allen V. and English, Jean M. "Recycling Gray Water for Home Gardens." University of Massachusetts. gray_water_for_gardens.html