Green Technology

Greywater Recycling

Not all wastewater is the same. Greywater—‘used’ water that has been diverted from the sinks and drains in your home, combined with reclaimed rainwater and then treated and filtered—can be reused to flush toilets, water lawns and do laundry. A greywater recycling system is energy-efficient, greatly reduces the impact on the city’s water system, and can save you a lot on your monthly water bill.

There are different types of greywater. Light-greywater comes from bathroom sinks, tubs, showers, laundry and can include rainwater.

Dark-greywater includes light-greywater, plus water from kitchen sinks and dishwashers. It contains food waste, grease and bacteria—as well as possible chemicals from household cleaners.

Black water is water that has come in contact with toilet wastes. It has to be chemically treated and disinfected before it can be reused.

Greywater collected from the house is diverted into a holding tank, often buried in the lawn, where it is filtered and treated before being sent back into the house for reuse.

Recycling greywater is still not legal in many municipalities across North America and it’s not a part of most building codes. There aren’t provincial or federal governmental guidelines for using greywater systems. Each individual municipality accepts—or rejects—proposed greywater systems that homeowners might want to install. But it can be done, and is being done, in many cities across North America.

A greywater system used to flush toilets and water lawns could save about 150 litres of drinking water per day, per household. That means that same amount of water is being diverted from the sewer system, reducing the strain on municipal sewer systems and treatment plants.