Much of the water used in a household for washing purposes simply goes down the drain but it can actually be put to better use to cut down on our water consumption and reduce the amount of water that makes its way to sewers. By installing a greywater purification system,  washwater  can be reused for irrigation and other household functions.

What is greywater?
Of the water that is used in a household for purposes other than consumption, about 60% of it is "greywater" (also called graywater) - water that is used for washing clothes, bathing, and showering. Unlike the unusable "blackwater" from toilets, kitchen sinks, and dishwashers that contains large amounts of organic matter, fats, and other additives greywater can be purified into reusable water quite easily through a filtration system.

Uses
Purified greywater is most commonly used for irrigation. In many parts of the world where water restrictions apply in dry seasons, greywater can be invaluable for the garden. This conserves precious drinking water in addition to easing the load on the city's wastewater disposal system.

Another use is to store the greywater and use it to flush toilets. Even with a low flush toilet, gallons of fresh water are drained with each flush.  Using the shower's greywater to flush the toilets in a home can save up to 20,000 gallons of fresh drinkable water each year, saving not only the environment, but also a good deal of money.

Installing a system
Greywater systems are readily available through many contractors. There are more than eight million greywater systems in the US and they have been around for more than sixty years. In many cases, the greywater treatment unit will be about the size of a hotwater tank. Some slim sized models are also available for installation inside walls.

These systems run about $1000 to $4000 depending on the age of the home and the type of system you want to install. Indoor-only systems are relatively low cost compared to outdoor systems. For more elaborate irrigation systems that automatically water your plants and trees, complex drip systems will need to be set up and this can cost upwards of $10,000. Some states require specific regulations be followed and even off offer rebates on certain types of greywater systems so it is best to check with your local water utility company for more information.

It is highly recommended that a system be professionally installed as improperly handled, greywater can produce odors, turn septic, or breed mirco-organisms. Under no circumstances should you drain untreated greywater into the soil as it contains detergents, soaps, oils, and other chemicals that have been washed down the drain.

Maintaining a greywater system
Greywater systems do require maintenance in the form of cleaning the filters every two to four weeks and adding chlorine cartridges every three months. The cost of running a greywater system is about $5-$25 per month depending on the size of the system. It is also important to keep in mind what you are pouring down the drain and phosphate-free products are recommended.

For more information about the use of greywater, check out greywater.net. There are also a variety of books about greywater systems used for irrigation available online including:

The New Create an Oasis With Greywater: Choosing, Building and Using Greywater Systems

Laundry to Landscape: A Simple, Efficient, Economical, Easy-to-Use Greywater System