City of Guelph Residential Grey water Reuse Feasibility Study

A residential grey water system

To find further ways to conserve its finite groundwater resources, the City of Guelph studied a residential greywater reuse system that flushes residential toilets with water from showers and baths. 

In the field test, 25 homeowners installed grey water recycling systems. Water quality, water consumption and energy usage were monitored for up to two years. While the overall satisfaction with the systems was high, many homeowners did not like cleaning the filters and grey water quality did not always meet Health Canada standards.

Flushing toilets with grey water can reduce household water use by up to 30 percent. But with decades-long payback periods, these systems are not financially attractive to homeowners.  Ironically, the presence of water-efficient fixtures in the home further reduces the savings possible from grey water systems.

The city is working to improve residential grey water reuse technologies and encouraging industry to continue to adopt water reuse technologies.

Results

Environmental Economic Social
  • Saving 16.6 L of water L per person per day
  • Making more sustainable use of the groundwater supply
  • Reducing  effluent going into the Speed River
  • Saving from reduced demand for treatment of water for household use
  • Saving from reduced volume of wastewater to be processed
  • Homeowners reported high satisfaction with the systems and few concerns about the safety of grey water

Challenges

  • Water savings were difficult to calculate, because some households did not produce enough grey water for toilet flushing and had to use varying amounts of potable water.
  • This dilution of the grey water by potable water affected samples.
  • Homeowners must be committed to the regular maintenance of the system.
  • Some homeowners find the colour and smell of grey water displeasing.

Lessons learned

  • Provide more training on the use and maintenance of the system to field test participants.
  • Develop a support network through education of tradespeople and contractors.
  • Provide rebates and other incentives to get residents to invest in these systems.

Resources

Partners and Collaborators

Project Contact

Wayne Galliher
Water Conservation Project Manager
City of Guelph, ON
T. 519-822-1260, ext. 2106

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