Greywater: the do’s and don’ts of reusing greywater at home


Catch your shower water in a bucket for later reuse. Photo credit: peasap

It’s winter in the Cape, and although I’ve enjoyed having a longer period of warm sunny days this year, even I have to admit that I’ve been hoping for a good wet winter after the drought. For a city right next to the sea, it’s amazing how we can be so affected by a drought season. But here we are, and as we look for ways to use less water, many are turning to greywater recycling. While this is great, greywater cannot be handled in the same way as municipal water, and health risks can arise from simple mistakes. If you’ve wondered about that smell as you water the lawn, or the colour of the water you’ve been storing, you may be doing something wrong with how you use greywater.

So firstly what is greywater? Greywater is any household wastewater, not including water from the toilet. Sometimes greywater is further sub-divided to give a dark greywater category. Water from your kitchen sink or dishwasher falls under dark greywater due to the higher levels of fats, chemicals and organic matter. Greywater differs from potable water in that it contains bacteria, and small particles, such as skin cells or hair. However, it provides a valuable and often untapped source of water that can be recycled to use less water – which is great both for droughts, and for your wallet!

Greywater is any household wastewater, not including water from the toilet.

Now, although it would be amazing to be able to reuse greywater in a built-in system, these can be expensive to install, or unfeasible for many reasons. However, even just using greywater to flush the loo and water your garden can halve your water consumption. Here are a few tips for safe and effective greywater reuse:

General pointers

  • Don’t store greywater for longer than 24 hours
    • If you do, bacteria will multiply, and your water will slowly turn darker, and start to stink.
  • Filter your greywater before reuse
    • Greywater often contains lots of particles so it’s best to filter it if you plan to put it through pipes
  • Don’t use greywater if someone has a contagious disease at the time
    • You do not want to be storing and spreading their germs!
  • Try to limit your contact with greywater
    • Because it contains bacteria, you want to limit your personal contact with greywater
  • Always wash your hands after using greywater

Bucket flushing with greywater

While it may seem easier to put your greywater straight into the cistern of the loo, this is not the best idea, since it may sit for longer than you expect, going fetid and even producing harmful substances. It’s better to bucket flush, unless you have a built-in greywater system.

Perhaps it’s the shape of our toilet bowl, but I must admit it’s taken me a while to master how to actually get the toilet to flush properly using a bucket full of water! Here’s a video if, like me, you have been struggling with this:


Greywater is a great source of water for your plants, but there are a few things to be aware of in how you use it!

  • Don’t use sprinklers with greywater
    • The bacteria in your greywater will end up in the air, and you might just breathe them, and make your household sick
    • Rather look at drip irrigation
  • Try not to water edible plants with greywater
    • If you do water edible plants with greywater, wash them in a solution with a germ-killing agent, eg: potassium permanganate, iodine, before you eat them
  • Greywater may be bad for your plants’ health if they like acidic soil
    • Although it is dependent on the soaps you use, greywater has a tendency to be highly alkaline, and can make acid-loving plants unhappy.

A final word of advice – don’t be neurotic about it, but exercise some caution, and realise that greywater is different from municipal water.

Moving away from greywater, if you can, why not think about rainwater harvesting?

More resources

If you’d like to look more in-depth at greywater reuse, there are some great resources out there:

Do you know how much water you are using? Check out this online water calculator from the City of Cape Town, and think about where you could replace potable water use with greywater.


One thought on “Greywater: the do’s and don’ts of reusing greywater at home

  1. Pingback: Rainwater harvesting – tapping into a greatly underused resource | Science Accessibly


Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s