Reusing greywater: benefits and problems

Bottle of greywater
Greywater. SuSanA Secretariat via Flickr

Greywater is used water coming from almost anywhere in your house except the toilet. Water mixed with human excrement is called blackwater. Therefore, if you wash diapers, you discharge blackwater from your washing machine for that load.

But with that exception, you make greywater when you use water in any sink, your bathtub, your washing machine, or your dishwasher.

You can reuse greywater. You don’t have to let it go down the drain. That way, you reduce the amount of fresh water your home uses and also the amount of wastewater you send to your sewer or septic system. 

Easy ways to  collect and reuse greywater

It is possible to install a collection system for your house, but first, here are some easier ways to collect and reuse greywater:

  • • When you cook in water, pour it into some kind of portable tub instead of down the drain.
  • When you rinse fruits and vegetables, rinse them in a tub of water instead of under running water. (Do that anyway to save running water.)
  • When you wash dishes by hand, run the dishwater into one tub (not directly into the sink) and the rinse water into another.
  • While you wait for hot water to start flowing from your tap, run water into a tub. 
  • If you want to recycle more water, you can take a sponge bath from a portable tub. Or use a bucket to empty the bathtub.
  • Or even detach a sink drain from the trap and let it drain directly into a bucket. If you do that, check the bucket frequently. It will fill in a hurry.

This greywater, then, has soap, detergent, food particles, FOG (fats, oils, and grease), dirt, hair, and other contaminants. If you install a collection  system, it also has microparticles from your washing machine—including, alas, polyester. 

And so you can’t drink, cook with, or bathe in it. What can you do with it?

  • Use it to flush toilets. Pour it into the bowl, not the tank.
  • Water houseplants with it.
  • Water your garden with it.

With all this organic matter in greywater, it attracts the attention of all manner of microbes. Use it the same day you collect it. Otherwise, the bad smell is only one problem with it.

Now, carrying a bucket of water outside is probably not something you’ll want to do very often. If you’re serious about using greywater for gardening or landscaping, you’ll need to install some kind of system.

Systems for greywater reuse

Greywater collection system
Greywater reuse system. Wikimedia Commons

You can install some kind of system where greywater flows from a fixture inside your house into a tank outside. You will reuse that water to irrigate your lawn, garden, or trees. It should include some kind of diverter valve for each sink and appliance so you can choose to store the water or let to go to the sewer or septic tank.

After all, if you launder diapers, the water becomes blackwater and must go to the sewer. If you use bleach, borax, or fabric softeners, water from that load will damage your plants.

But most of the dissolved organic matter in greywater contains nutrients that benefit them. You can use less fertilizer––if any.

I assume most readers won’t want to bother with greywater reuse systems, so I won’t attempt to explain them. You can use my sources or advertised books below as a starting place for your own investigation.

Here are some caveats:

  • First, the simpler the better. Avoid systems that require pumps, filters, or other high-maintenance components unless they’re absolutely necessary. 
  • You will need to find what your local zoning ordinances require, get all necessary permits, and all the other legal rigmarole.
  • Don’t let the water form pools in your yard or garden. Disperse it over large areas. 
  • Greywater is alkaline and so not good for plants that require acid soil. 
  • Don’t use a sprinkler with it. It shouldn’t get on edible parts of plants. For that matter, don’t reuse it at all on carrots, radishes, or other root vegetables you intend to eat uncooked. You’ll use hoses, which you should be prepared to move frequently. 
  • Gardening and watering the lawn are seasonal activities. Greywater accumulates year-round. Don’t collect what you can’t reuse the same day.

Shop related products

Rain Barrel, DIY Kit, Used Food Grade Barrel, Upcycled, 58 Gallon Size

The New Create an Oasis with Greywater 6th Ed: Integrated Design for Water Conservation, Reuse, Rainwater Harvesting, and Sustainable Landscaping / Art Ludwig

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

About greywater reuse / Greywater Action
How to reuse grey water in the home and yard / Derek Markham, Treehugger. June 2, 2014
Safe use of household greywater / New Mexico State University College of Agricultural, Consumer, and Environmental Sciences

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