Greywater systems.

Greywater is any water that you use in your home except toilet water. Shower, sink and laundry water are types of greywater and can be reused for other purposes, mainly irrigation for landscaping. The aforementioned waste water accounts for up 50-80% of water wasted by residential users.
Greywater systems work by diverting water for usage in other areas. These systems can be a part of new construction or retrofit on an existing home. There are two main ways to recycle greywater: those that recycle with purification and without. Those that use a filter to purify the water can be designed into existing plumbing on a home. They often contain a pump to send water to toilets for flushing or outside for irrigation.
There are several benefits to reusing greywater.
Saving fresh water.
Using greywater for applications such as watering the garden or landscaping can save you money and increase the local water supply. Especially in the summer and dry climates, water usage is evenly split between indoor and outdoor. If you could recycle indoor water for use outdoors, it could cut your water usage by nearly 50%.
Extended life of a septic tank.
Greywater use can significantly extend the life of your septic tank by putting far less strain on the system. The same goes for your municipal water treatment systems, less wastewater flow results in higher efficiency and lower costs.
Purification.
Water is very efficiently purified in the upper, most active region of soil. This protects the quality of natural ground waters.
Plant and soil benefit.
Use of a greywater system enables a landscape to blossom in areas where water may not otherwise be available to support plant growth. Also, nutrients that still exist in your wastewater would find their way back into your yard and help to maintain the land’s fertility.
Sensitivity to natural cycles.
A greywater system provides satisfaction in taking responsibility for the wise, ecological use of a valuable resource. It also saves energy by reducing pump and treatment needs. It will also increase your awareness of what goes down your drain; knowing that the water is returning to your land you are far less likely to toss toxic chemicals down the drain.

There are, nonetheless, possible health and environmental risks to using greywater if it is not done safely. Water that is laced with harsh, household chemicals can do harm to you and possible kill the very plants you are trying to care for.
Be sure never to use water from the toilet and kitchen. Kitchen water is easily contaminated with grease, bacteria, and chemicals. Don’t use harsh, toxic cleaners if you have a greywater system. Look for phosphate-free or low phosphate cleaners. Also, when using a greywater system, it is best to use sub-surface irrigation pipes because it is low risk and the soil will filter the water. Hosing your garden or landscape with greywater puts you at high risk of contamination from any existing chemicals or bacteria.
Finally, because of the potential health risks involved in using greywater, many states and cities have strict codes or laws regulating its use. Check with both your local building department and a qualified plumber before installing a greywater system.