Gray Water & Rainwater Harvesting

Boston, MA: A six-alarm fire on October 17, 2011 devastated Wardman Apartments in Roxbury, one of 16 affordable housing developments developed and co-owned by Urban Edge. There were no fatalities due to the courageous actions of residents and firefighters. But thirteen people were injured and more than 75 residents became homeless.

Urban Edge was able to clean up some of the affected units to allow for a number of families to return to their homes by the end of 2011. However, because the fire required immediate demolition of the 71 Westminster Avenue section of the building where twelve families lived, those families were temporarily housed in other units elsewhere.

The reconstruction of 71 Westminster Avenue is now complete and the families have returned. In keeping with Urban Edges sustainability standards, the new building exemplifies the best in green affordable housing.
::: Read the complete story in the Press Release here :::


In the Unites States, approximately 340 billion gallons of freshwater is used each year to support residential, commercial, agricultural, industrial, and recreational activities. Heavy water usage increases operational costs for building owners and municipal supply and treatment centers. Reducing water usage helps conserve our environment’s water resources and helps stabilize municipal taxes and water rates. Gray water and rainwater harvesting systems are two types of water efficiency systems.

Urban Edge Guidelines

There are several important issues to review when considering these water efficiency systems.

  • Determine whether local utilities and health officials allow such a system. In Massachusetts the state allows gray water systems while some municipalities may not. As of 2005, the city of Boston does not have a set policy for gray water systems. The city recognizes that there are such systems in the city, following state code, however the city does not have its own regulations. Then look at possible end uses such as toilet flushing and irrigation. Regulations come into play, as most states allow only underground irrigation (no sprinklers) with gray water.
  • Consider whether it’s economically viable to change the property’s plumbing system. This usually requires major structural work and is unlikely to be viable in older mid- and high rise properties unless a major renovation is under way but will be more cost effective for new construction. The Cost of gray water systems are very site-specific, and in all cases relatively high when compared to some more typical cost–effective retrofit alternatives. For new developments, pre–plumbing for gray water ranges from just adding a few extra plumbing Y’s at various locations to placing additional supply lines or even mains throughout the building, for very large installations. Also, be sure you have space available for a storage tank and filter.
  • Cost Effectiveness: Gray water or rainwater harvesting systems should be compared to other water and sewer reduction strategies that may require significantly less infrastructure. Dual-flush toilets, waterless urinals, ultra-low flow faucets and shower heads, for example, all cost significantly less than gray water systems and do not require the additional space and equipment for items such as storage tanks, separate piping systems, filtering, and treatment, etc.

Spotlight on Urban Edge

Urban Edge does not currently have any gray water systems but we are considering these alternatives for future projects.

Options and Criteria Review

Gray Water System
One water efficiency strategy involves the use of gray water systems. The gray water recovery system reuses wastewater from sinks, showers, and laundry for non-potable uses such as flushing toilets and/or irrigation purposes. Water from urinals and toilets is known as “blackwater” and cannot be safely reused for other purposes. A typical household can recover 50 to 100 gallons of water per day using a gray water system.

There are several methods used to treat gray water ranging from settling tanks, disinfectants and filters. Gray water is treated to remove solids, prevent odors, and eliminate other health hazards. Food coloring is often added to gray water so that wherever it appears throughout a building it is immediately recognized as non-potable. In addition, if used within a building a separate water supply piping system is typically required. This system is painted a different color from the potable water supply piping system to keep future plumbing changes from accidentally tying into the gray water system.

Rainwater Harvesting System
A second type of water re-use system is a rainwater harvesting system that uses rainwater runoff collected from the roof of the building or the site to replace other potable water use either for irrigation or for toilet or urinal flushing. Water collected off the roof is typically considered “clean” instead of gray water from showers or sinks. It is not considered potable since it has not been chlorinated or treated in other ways the municipal water supply is usually treated. Most municipalities will allow rainwater to be used both in spray-head irrigation systems as well as within buildings for toilets.