Rainwater vs. graywater

People often use rainwater and graywater [or greywater] interchangeably. They are not to be confused with one another as they are two very different types of water with very different characteristics.

Rainwater is water that is generated from a precipitation event, while graywater is generated from dishwashing, clothes washing, general sink usage, and bathing. Please note that if graywater has high levels of food waste, certain harsh chemicals, or you-know-what [Doodie], it can no longer be classified as graywater and would be considered black water [not to be confused with the water referenced in the Doobie Brothers song of the same name].

Rainwater is high quality water that is just beneath U.S. drinking water standards only because of the low level of contaminants it picks up in the air and through its conveyance. Graywater has detergents, small food particles, and other pollutants picked up through its usage.

Rainwater can be used for any type of water demand depending on the level of filtration or purification. With basic filtration removing the particulates, rainwater is suitable for storage and use for any nonpotable need, such as irrigation, toilet flushing, clothes washing, pool and pond refilling, auto and building washing, cooling towers, and fire suppression. If purified using the proper systems, rainwater can be used for potable needs, such as drinking, cooking, and bathing.

Graywater can be used for subsurface irrigation if used immediately and the local codes allow this, however federal law prohibits the use of grey water for above ground irrigation. With the use of graywater recycling systems graywater can be used for toilet flushing and clothes washing in the home, however It cannot be purified and used for potable water needs. Graywater should not be stored without first being treated, because its contaminates decompose so quickly.

Well designed rainwater harvesting systems using the highest quality products require very little maintenance. Graywater recycling systems require constant maintenance and repair.

The main benefits of a graywater recycling system are the reduction in the amount of water going into our sewer system and the conservation of our water resources. The benefits of rainwater harvesting systems include the conservation of our water resources, a significant reduction in pollution of our waterways, and the reduction or elimination of storm water runoff.

As you can see, these are two very different types of water. Both are beneficial to our environment and will play an important role in how we handle this important natural resource in the future. As water is quickly moving up the list of important issues our country and world must deal with, these systems will continue to improve and ultimately become a normal part of existence.