Requirement Summary
This measure can be claimed if there is a grey water recycling system that treats the waste water from the building, except the waste water from toilet flushing and kitchen sinks. This recycled water must be re-used on the project site to replace water consumption from the municipal water supply. End uses may include flushing toilets, the HVAC system, cleaning the building, or irrigation of landscaping.
Intention
By recycling the grey water, the use of fresh water from the municipal supply can be reduced. The load on the local water and sewage infrastructure is also reduced.
Approach/Methodologies
EDGE assumes that the recycled grey water will be used for flushing toilets. When this measure is claimed, EDGE automatically calculates the potential supply and reduces the municipal water demand for flushing toilets by that amount. EDGE assumes that wastewater from the building is collected and stored in sufficient quantities to meet the demand for flushing toilets. If the quantity of treated grey water is insufficient, then only a portion of the demand is shown to be met by the treated water.
A water balance model can be produced by the design team to demonstrate the potential for water recycling.
The recycled water must be reused for flushing toilets, with the remainder directed towards other uses. Where this water is not used for toilet flushing, the project must provide additional documentation that the system is indeed replacing municipal water supply. For example, if the recycled water is being used for irrigation only, then the project must demonstrate that (a) the landscaped area requires municipal water (in addition to just natural rainwater), and (b) the system is designed to serve the landscape, thus replacing water from the municipal supply. This can be done with drawings of the plumbing layout at the design stage, and with pictures that show the planned piping system connected to the irrigation system at the post-construction stage.
Potential Technologies/Strategies
When recycling the water, a dual piping system must be used to separate the recycled water from the mains.
Treated water must be in accordance with local or international health and sanitary code requirements (whichever is more stringent).
In some cases, the grey water treatment plant can be centralized for a combination of buildings within the development. In these cases, the central plant must fall within the site boundary of the project, or managed by a company within the control of the site owner. This is to ensure continuity of sustainable management and future access to the system for maintenance.
However, when the grey water treatment plant is located off-site, then a contract with the management company in charge of water treatment must be provided as part of the documentation at the post-construction stage.
Some jurisdictions may not permit the use of grey water in buildings for flushing; in such cases this measure cannot be claimed.
Relationship to Other Measures
The quantity of wastewater available depends on the efficiency of water fittings; more water-efficient buildings may have insufficient water available to completely offset the demand for flushing. This measure has an impact on “Other” Energy uses in the energy chart as water pumps required for operation of the system are included in in that category.
Assumptions
The base case assumes that there is no grey water recycling. The improved case assumes that grey water from the washbasins is reused in the building for flushing water closets.
Compliance Guidance
| Design Stage | Post-Construction Stage |
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At the design stage, the following must be used to demonstrate compliance:
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At the post-construction stage, the following must be used to demonstrate compliance:
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