Indoor Water Efficiency

Seventy percent of potable (drinking) water is used in U.S. homes. LEED aims to reduce the amount of potable water used indoors, reducing buildings' environmental impact and removing some of the burden from municipal water supply systems.

A great deal of potable water is used indoors, with Americans using about 70% of their water inside their homes, according to the US EPA.  In fact, the American Water Works Research Foundation performed a 1999 study in which they found that Americans use 26.7% of indoor water in the toilet, 21.7% in the clotheswasher, 16.8% in the shower, and 15.7% from faucets.  Nearly 14% is attributed to leaks and 5.3% is from other sources. 


Therefore, indoor water efficiency is incredibly important for conserving potable water resources and alleviating the burden on the municipal water supply.  LEED encourages using water efficient appliances as well as replacing potable water with recycled graywater or rainwater.


Free LEED GA Practice ExamEfficient Appliances and Fixtures


In LEED 2009, the Indoor Water Use Reduction prerequisite mandates that all projects use water fixtures and fittings that reduce water use by 20% below a baseline.  There are many fixtures available on the market that use 20-50% less water than the specified baselines.  In fact, appliances like waterless urinals use no water – a large improvement over the 1.0 gallons per flush standard.


LEED 2009 recommends that projects use WaterSense labeled products.  WaterSense is an Environmental Protection Agency Program that labels high-performing, water efficient products.  Since the program started in 2009, it helped consumers save 4.8 billion gallons of water and over $8.9 billion in utility bills.


Graywater Recycling & Rainwater Capture


LEED 2009 awards two points to projects that reduce potable water use by 50% through water efficient fixtures OR nonpotable water.  Nonpotable water includes recycled graywater, captured rainwater, or municipally treated wastewater.


Graywater recycling is capturing water from wash basins, showers and baths and using it in nonpotable functions, such as toilet flushing and irrigation.  This process does not reduce the amount of indoor water use, but rather reduces the amount of potable water used indoors. Graywater recycling is much easier than blackwater, or toilet water, recycling, because it requires little or no purification.  On the other hand, blackwater must be significantly treated before reuse.


Rainwater harvesting is the capture of rainwater for use either indoors or outdoors.  A rainwater harvesting system can be as simple as a bucket with a hose attachment, or as complex as a roof system with downspouts, pumps, roof washers and pressure tanks.  Simple systems usually reuse the water outdoors, while others will direct it to toilets for flushing, or treat it for potable applications and drinking water.


Both graywater and rainwater recycling reduce the demand for potable water and decrease the energy needed to treat the water at a municipal facility.


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