Every day in restaurants across Toronto, thousands of litres of clean drinking water is flushed down the drain—without ever being used for its intended purpose.

Treated by the city, potable water is safe to be consumed. It’s the same water that flows from your taps, but it’s also the water that is typically found in toilet cisterns.

For advocates of greywater recycling systems, it’s a use that doesn’t make sense, especially when there is other water available. Also called “sullage,” greywater is wastewater that has been captured from drains and reused, typically in toilets and subsurface irrigation. Unlike the forebodingly named “blackwater, ” it doesn’t contain toxic chemicals or fecal matter and is safe for use in washrooms.

Homeowners throughout Toronto have begun to install greywater recycling systems but only a handful of government and commercial buildings, such as Waterfront Toronto and the Evergreen Brickworks, are making use of the green technology. John Bell, co-Founder of HTO Water Technologies, a supplier of greywater recycling systems, says that this is a missed opportunity.

“The greatest impact is when there’s a high volume of people flushing toilets,” Bell says. In residential buildings, toilets are the single greatest culprits of water waste.

Although this may not be the case in restaurants, where water consumption is the result of cleaning and food preparation, the high-traffic nature of their restrooms is exactly what makes them prime candidates. If 200 diners per day were to each use the washroom, it would mean 1200 litres of water simply being flushed away.

Environmental concerns aside, installation of a greywater recycling system could result in up to 40 per cent off your next water bill. “The savings would be excellent,” says Bell. He should know—in 2011, Bell, formerly the host of HGTV’s World’s Greenest Homes, completed his own dream eco-home, which includes a greywater system.

While the potential cost savings from operating a greywater recycling system are substantial, there are a number of key installation considerations:

  • What greywater sources are available? Bell says that the single greatest concern for restaurants is ensuring that there is enough water to supply the toilets. Unlike homes, where bathing water is the primary source of greywater, restaurants would have to rely on washbasins, lavatory sinks and dishwashers. (Due to oil, grease and food, kitchen sinks are not candidates for capturing greywater.) While city water serves as a backup, finding a secondary source of greywater ensures that the system reaches its maximum efficiency. Installing a rainwater harvesting system would serve this purpose.
  • Are you willing to complete the necessary retrofits? Water storage tanks are typically installed in a facility’s basement. To capture the greywater, drains will first need to be isolated and dedicated supply lines will need to run to the toilet. In addition, installing dual flush or low-flush toilets will increase the capacity of your greywater system.
  • Do you have time for maintenance? Greywater recycling systems require some maintenance, which will mean adopting a monthly cleaning schedule. The tank’s filter will need to be cleaned regularly and chlorine tablets will need to be dropped into the tank to prevent bacteria growth and the accompanying odour. (Supplementary chlorine tablets may also be dropped directly into toilet cisterns to prevent any smells.) Finally, once per year, the tank will need to be flushed out to prevent residual build-up.
  • Are you concerned about appearance? Greywater may look a little murkier to the naked eye, although with proper cleaning and maintenance it shouldn’t smell. “You can see a difference, but it’s nothing visually alarming,” says Bell. If appearance is cause for concern, many commercial institutions elect to add a dye tablet to their greywater to distinguish it from city water.

Want to learn more about other ways of conserving water? Check out our article about saving water in your restaurant kitchen.