What You Need to Know about Using Greywater

What is grey water? 

Greywater is the recycling of bath, shower, hand basin and laundry water, which can then be used to irrigate your garden. This is especially relevant for South Africans as they have to contend with low rainfall, water shortages and water restrictions. 

By reusing bath and laundry water, homeowners can keep their gardens looking healthy - even in times of drought - without spending an extra dime on their water bill. 

Plus, grey water also contains nutrients derived from the residues and soaps in the water, which feed and nourish the soil to produce lush plants. 

Do not, however, use water waste from the kitchen sink as this contains fat content that will damage your garden. 

Greywater systems 

A grey water system can be as simple as using a bucket to carry the waste water outside, or as complicated as having the greywater piped directly outside using a tank and pump. 

According to Water Wise, a simple bucket system can be used to transport the greywater, by hand, from the bathroom to garden. It is the cheapest system, but is inconvenient and increases the possibility of contact and contamination between the greywater and people carrying the bucket. 

Homeowners can also make one themselves by connecting a pipe from the outlet of their bathroom to a hose pipe. 

Alternatively, homeowners can invest in a system that connects the greywater to the outlet pipes of the bathroom where the greywater will be collected or stored in a tank. The water will run through a hair and lint filter first before it is pumped out through irrigation pipes to the garden. 

With any greywater system, it is important that you use ‘garden friendly’ products and detergents that do not contain any salts, boron or bleach. 

If you intend on using the water to feed a vegetable garden, it is important that the system has a filter. 

How much does a grey water system cost? 

According to Erika Theron from Rainwater Harvesting, a small, entry-level system that works instantly (no storage) could cost around R13 000 (fully installed), while a system that offers European Bathing filtration standards could cost R110 000-plus. She says in between these there are different options that homeowners can choose from. 

Greywater tolerant plants 

In general, tough drought-tolerant plants will do best with greywater irrigation watering. 

Generally, greywater is alkaline, so avoid using it on plants like azaleas, begonias, gardenias, hibiscus, camellias and ferns. Avoid using it on fynbos and proteas too. 

Plants that flourish from greywater include olives, rosemary, bougainvillea, lavender, Cape honeysuckle, Italian cypress, bearded iris and petunias. 

To help these plants thrive, occasionally flush the plants with a bit of rainwater or tap water to remove the residue from the greywater. 

Greywater reuse guidelines 

Homeowners who’d like to use greywater in their gardens should be aware of the hygiene factors. Because greywater is not fresh, homeowners should apply the following to avoid the growth of bacteria and unpleasant odours… 

1. Use the greywater within 24 hours. Storing the water any longer will result in a bad odour. 

2. Minimise contact with greywater. 

3. Use non-toxic cleaning agents and products where possible.

4. Do not allow your greywater to pool on the surface of the soil. Standing water will provide a breeding ground for mosquitoes.

5. Do not use water from the kitchen or toilet.

6. Do not use laundry water that has been used to wash nappies.

7. Do not allow children or pets to drink or play in greywater.

8. Do not let greywater run into the swimming pool.

9. Do not use greywater if a family member or someone on the property has an infectious illness.

Image courtesy of Property24