What is Greywater? And How Can You Use it At Home

Greywater is the wastewater from baths, showers, washing machines, dishwashers and sinks that is no longer drinkable but could have other uses such as flushing toilets.

It is estimated that greywater makes up 50-80% of the household’s wastewater.

Greywater systems collect this wastewater, filter it and pump it into a storage system. It is then used when needed in areas of the house such as flushing the toilet and watering your garden.

Watering Plants with Greywater

Greywater can not only be good for the environment and help reduce your water bill, the traces of dirt, food, grease, and hair (which become pollutants when released into bodies of water) are nutrients and can be valuable fertilisers for your plants.

Greywater for Direct Use

This is the simplest way to reuse greywater as it requires no filtration system, meaning little maintenance.

The water can be used for irrigating lawns, ornamental gardens, or trees. If you are using it for your vegetables, don’t let it touch any edible parts of the plant.

Moreover, never store greywater for more than 24 hours as it will cause foul smells.

If using the direct method you will need to be able to match the greywater produced to your plant’s irrigation needs. We recommend installing a 3-way valve so wastewater can be switched between the greywater system and the sewer/septic.

There are two ways to use greywater directly for irrigating your garden:

  • Laundry Drum – this is a cheaper option which would be useful if you rented your home or had a lot of hard terrain (e.g. concrete, patio) between your washing machine and the area you want to irrigate. The water from the washing machine is pumped into temporary storage (the drum) which drains out the bottom into a hose that can be moved around to water where necessary. This requires you to manually move the hose to the areas you need watered.
  • Laundry-to-Landscape – Invented by Art Ludwig and explained by Greywater Action, the Laundry-to-Landscape solution is fairly cheap and easy to install. The slight pressure from the washing machine’s internal pump means the greywater can be pumped across a relatively flat surface without altering household plumbing. The washing machine drain hose is attached directly to a diverter valve that allows you to switch the flow of wastewater between the sewer/septic and the greywater irrigation system. The greywater irrigation system directs water through 1″ tubing with 1/2″ outlets directing water to specific plants. Greywater Action suggest this as the number one place to start when choosing to reuse greywater.
A laundry-to-landscape greywater system. Image courtesy of GreywaterAction.org via CleanWaterComponents.
A laundry-to-landscape greywater system. Image courtesy of GreywaterAction.org via CleanWaterComponents.

Constructed Wetlands

If you are producing more greywater than you need for your garden then constructed wetlands are a biological filtration system which means you will be able to store the greywater for longer.

Wetlands are a natural way to filter greywater as the plants absorb nutrients and particles are filtered from the wastewater to make it safe for storing.

For wetlands in your garden Greywater Action recommend reedbed systems in bathtubs filled with gravel, mulched with woodchips, and planted with cattails, bulrushes, and other wetland plants.

Schematic of the Vertical Flow Constructed Wetland. Source: TILLEY et al. (2014)
Schematic of the Vertical Flow Constructed Wetland. Source: TILLEY et al. (2014)

Things to Note About Greywater Systems:

  • Typically water from kitchen sinks and dishwashers is not reused as the detergents used to wash dishes can be harmful to plants. However, if you manage to replace your detergents with ones free of salts and boron the wastewater can be reused.
  • If you have a water softener, the greywater may not be suitable for plants due to the salts. Consider a potassium instead of a sodium softener.
  • Ensure soaps and products used are biodegradable and non-toxic to keep the greywater suitable for use on your plants.
  • When using greywater for your plants Greywater Action suggest keeping the system as simple as possible to avoid costs and high levels of maintenance.

For Flushing Toilets

It’s estimated that flushing toilets accounts for a third of household water usage, meaning you could reduce your usage and bill by using greywater to flush your toilets. Whilst these are slightly more complicated to install and require you to front the cost initially, Waterscan suggest that the system can pay itself back in 3-5 years.

Whilst Waterscan stress that the systems should be fitted prior to constructing a building and are best suited to businesses, many companies offer residential water treatment system in homes on new estates and retrofitted into individual homes throughout the UK.

If you’re interested in installing a greywater system, check out our recommendations.

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