Greywater systems collect used water from non-toilet fixtures, such as sinks, showers and washing machines, and reuse it for other applications, such as irrigation or toilet water. Some greywater systems treat the water before it is reused, and others do not.

The following three greywater systems are currently available on the market and can potentially contribute to green building and LEED projects.

1. Aqua2use
Aqua2use offers a graywater treatment system that purifies a building’s graywater for reuse both indoors and outdoors. The graywater, which is collected from the shower, laundry, and dishwasher, is purified with both biological and mechanical filtration, then disinfected with UV-C. This purified graywater can then be reused for the toilet, laundry, and irrigation.Aqua2use graywater reuse products are designed, manufactured and patented by Matala Water Technology, a company based in Taiwan.

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Aqua2use claims that their graywater treatment system can save 30 gallons per person per day – or up to 40,000 gallons a year for a family of four.

Aqua2use’s graywater systems were rated as one of BuildingGreen’s top 10 green building products of 2012.

2. Sloan AQUS Water Reuse System

Sloan’s AQUS Water Reuse System (pictured) collects graywater from the sink, passes it through a sanitizing device, and transports it to a reservoir under the sink. When the toilet it flushed, the treated water in the reservoir moves into the flush tank for reuse.

According to Sloan, the AQUS can save up to 6000 gallons of water per year.

The AQUS system requires annual maintenance, does not cross with the fresh water system, and does not inhibit backflow prevention.

According to Sloan, the AQUS is compatible with two piece toilets from many manufacturers, including Kohler, American Standard, TOTO, Mansfield, Gerber, Eljer and Western.

The AQUS was listed by Sustainable Industries as one of the top 10 green building products of 2010.

3. Clivus Multrum

Clivus Multrum was founded in 1962 by Swedish engineer Rikard Lindstrom, who developed the first composting toilet. Since its incorporation in the U.S. in 1973, Clivus Multrum has manufactured composting toilets and greywater systems.

Clivius Multrum offers a greywater system that collects water from all non-toilet fixtures (e.g., sinks, showers, washing machines). Most of the company’s systems do not filter this water, but rather channel it directly to outdoor or indoor irrigation systems, where the plants uptake the water and its nutrients.

The systems are custom designed by the company for site-specific conditions.

LEED Credit Overview

Graywater systems could contribute to LEED in the Water Efficiency credit category of the LEED for New Construction (NC) rating system. These products could specifically contribute to the following credits in LEED NC:

Water Efficiency (WE) Prerequisite 1: Water Use Reduction (0 points)

This prerequisite requires that the LEED project use 20% less water than the baseline calculation. Since graywater can be reused, such as for flushing toilets, treatment systems could contribute to this prerequisite.

WE Credit 1: Water Efficient Landscaping (2-4 points)

This credit requires a 50% reduction (2 points) or 100% elimination (4 points) of potable water used for irrigation. Since some systems reuse graywater for irrigation, they could contribute to this credit.

WE Credit 2: Innovative Wastewater Technologies(2 points)

This credit aims to reduce wastewater and potable water demand. Two points are awarded for either reducing potable water use for sewage conveyance by 50% OR by treating 50% of wastewater on-site to tertiary standards*.

*According to LEEDuser, “tertiary treatment is the highest form of wastewater treatment and includes removal of organics, solids, and nutrients as well as biological or chemical polishing, generally to effluent limits of 10 mg/L biological oxygen demand (BOD) 5 and 10 mg/L total suspended solids (TSS)”.

WE Credit 3: Water Use Reduction (2-4 points)
This credit is the same as WE Prerequisite 1, except the required percentage of water use reduction is higher. Projects can earn 2 points for 30% water reduction, 3 points for 35%, or 4 points for 40%.


imageDavid M. Pratt

David M. Pratt, P.E., CEM, LEED AP is an Energy Management Consultant for Sustainable Climate and Energy Solutions group of MWH Americas, Inc.
MWH is the global leader of the wet infrastructure sector. The MWH organization is driving the wet infrastructure sector globally, and we are leading the world in results-oriented management, technical engineering and construction services to build a better world.

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