Water Reuse & Indoor Water Use

Michael Cross

Water Efficiency (WE)

The Water Efficiency category makes up one of the categories scored under the LEED rating system.  The main purpose for the Water Efficiency category is to reduce the wastefulness of water.  Subcategories that are found under Water Efficiency are Water Reuse, Irrigation System, and Indoor Water Use.  There are specific criteria that must be met for LEED certification points to be awarded under these subcategories.  The subcategories that make up Water Efficiency account for 15 maximum points towards the LEED rating system.  The minimum that must be met under Water Efficiency as a whole, to qualify for a LEED certified home, is 3 points.  A LEED certified home that meets the requirements set under Water Efficiency is designed to limit wastefulness of water by reusing graywater and installing water conserving fixtures.  It is also designed to harvest rainwater for use in and around the home.

1. Water Reuse

The first sub-category under the Water Efficiency section of LEED is water reuse.  This sub-category determines how much water can be reused in and around the LEED certified home.  The first item that can be scored under water reuse is a rainwater harvesting system.  This can also be combined with a graywater reuse system, or the use of a municipal recycled water system.  The combination of the rainwater harvest system and either the graywater reuse system or use of municipal recycled water system can account for a total of up to 7 points.  I will be discussing Graywater reuse systems in the LEED certified home.

1.2 Graywater Reuse Systems

Graywater is usually defined as: wastewater generated from domestic activities such as laundry, dishwashing, and bathing which can be recycled on-site for uses such as landscape irrigation, and constructed wetlands.  An average four person household sends well over 38,000 gallons of reusable water down the drain each year from bathrooms and laundries.  Graywater gets its name from its cloudy appearance and from its status as being between fresh potable water (known as white water) and sewage water (known as black water). In a household context, graywater is the leftover water from baths, showers, hand basins, and washing machines only. Any water from any contaminating sources such as toilets is considered black water.  The state of Illinois allows gray water usage, providing that the water is treated and used in accordance with environmental and health standards.  Illinois passed the Water Use Act in 1986, although the act focused primarily on the withdrawal of water from the ground, it also set a precedent for the states’ outlook on water usage.  The act illustrated the states’ view that it is in the public interest to better manage and conserve water.  The act also established a means for reviewing potential water conflicts.  The formation of this act eventually changed the perception of gray water use.  According to the state, the intent of gray water is to save clean water for human consumption by fulfilling the need for water in residential and industrial areas.  The goal of the Graywater sub-category under water reuse is to award home owners with LEED points that take advantage of reusing graywater in and around the home.

According to the LEED certification checklist there is a specific standard that must be met in order to receive the point under the graywater subcategory.  It says you must:

Design and install a graywater reuse system for landscape irrigation use (i.e., not a septic system) or indoor water use. The system must include a tank or dosing basin that can be used as part of the irrigation system. Graywater must be collected from at least one of the following: clothes washer, showers, some combination of faucets and other sources estimated to exceed 5,000 gallons per year.

The most common method of graywater reuse is to install a graywater reuse system in the home that collects the graywater and keeps it separate from the black water in the sewage system.  There are two common types of graywater reuse systems; gravity fed manual systems and package systems.  The manual systems do not require electricity or pumps because they work on gravity taking the graywater to the area needed.  They may require a larger yard area to install the system outside.  Packaged systems require electricity but are self-contained and can be installed indoors.  With each option codes and local ordinances should be considered.

One of the main questions associated with graywater reuse and graywater reuse systems is why?  Why would people want to put dirty water on their lawn and/or garden? Most people just assume use fresh water to water their lawn and garden.  Well, in many parts of the country fresh water is scarce, especially during the hotter seasons of the year. Lawn watering contributes a great deal too freshwater depletion. Lower reservoirs, wells and rivers result from increased fresh water usage.  One must consult their local ordinances before installing a graywater system in their home.  In some places throughout the country these types of systems are not allowed for fear of contamination.  It is though becoming a more widely accepted practice.

3. Indoor Water Use

The subcategory entitled indoor water use sets LEED standards for indoor water fixtures designed to conserve water during everyday use.  These fixtures would include; lavatory faucets, shower heads and toilets.  There are two subcategories under indoor water use which are; high-efficiency fixtures and fittings and very high-efficiency fixtures and fittings.  Under the high efficiency subcategory 1 point can be award for each of the three criteria’s for a total of 3 points.  Under the very high- efficiency subcategory 2 points can be awarded for each of the three criteria’s for a total of 6 points.  A project cannot earn points in both WE 3.1 and WE 3.2 for the same fixture type (i.e. faucet, shower, or toilet).

3.1 High-Efficiency Fixtures and Fittings

In this category the project can meet one or more of the following requirements by installing high-efficiency (low-flow) fixtures or fittings, to earn LEED certified points in the following areas.

a) The average flow rate for all lavatory faucets must be ≤ 2.00 gpm (gallons per min)

b) The average flow rate for all showers must be ≤ 2.00 gpm per stall.

c) The average flow rate for all toilets must be ≤ 1.30 gpf (gallons per flush) OR toilets must be dual-flush and meet the requirements of ASME (American Society of Mechanical Engineers) A112.19.14  OR toilets must meet the U.S. EPA WaterSense specification and be certified and labeled accordingly, but cannot be earned through the use of toilet tank bags.

3.2 Very High-Efficiency Fixtures and Fittings

In this category the project can meet one or more of the following requirements by installing very-high efficiency fixtures and fittings to earn LEED certified points in the following areas.

a) The average flow rate for all lavatory faucets must be ≤ 1.50 gpm OR lavatory faucets must meet the U.S. EPA WaterSense specification and be certified and labeled accordingly.

b) The average flow rate for all showers must be ≤ 1.75 gpm per stall.

c) The average flow rate for all toilets must be ≤ 1.10 gpf, but again cannot be earned through the use of toilet tank bags.