The intent of this credit is to reduce the amount of potable waterPotable water meets or exceeds EPA's drinking water quality standards and is approved for human consumption by the state or local authorities having jurisdiction; it may be supplied from wells or municipal water systems. used for flush fixtures and to minimize the amount of wastewater conveyed to the municipal system. For credit compliance, you have two options:
Option 1: Reduce the quantity of potable water used for flush fixtures (water closet and urinals only) by 50%. You have two ways to make this reduction:
Option 2: Treat 50% of wastewater onsite to tertiary standards and infiltrate it, or reuse the treated wastewater onsite.
To determine your percentage reduction, compare a baseline case with the design case. Note that the baseline for WEc2 is not the same as the baseline for WEp1 and WEc3: Water Use Reduction. Whereas WEp1 and WEc3 count flow (shower, lavatory and kitchen sink) and flush fixtures (toilets and urinals), WEc2 only counts toilets and urinals. The data that you enter on flush fixtures in the LEED Online credit form in WEp1 will automatically populate the credit form for WEc2.
The calculations for wastewater use are based on the number of full-time equivalentFull-time equivalent (FTE) represents a regular building occupant who spends 40 hours per week in the project building. Part-time or overtime occupants have FTE values based on their hours per week divided by 40. Multiple shifts are included or excluded depending on the intent and requirements of the credit. (FTEFull-time equivalent (FTE) represents a regular building occupant who spends 8 hours a day (40 hours a week) in the project building. Part-time or overtime occupants have FTE values based on their hours per day divided by 8 (or hours per week divided by 40). Transient Occupants can be reported as either daily totals or as part of the FTE. Residential occupancy should be estimated based on the number and size of units. Core and Shell projects should refer to the default occupancy table in the Reference Guide appendix. All occupant assumptions must be consistent across all credits in all categories.) occupants. FTE calculations can sometimes be confusing in certain building types or occupancy types—see WEp1 for more information.
Generally, the easiest and cheapest way to achieve this credit is to install low-flow and waterless fixtures. Using waterless urinals or pint-per-flush urinals in combination with ultra-low-flow toilets (1.0 gpf) or aggressive, dual-flushA type of water-saving toilet that gives a choice of flushes depending on the type of waste solid or liquid. toilets (1.28/0.8 gpf) can work, although it depends on your project occupancy and will need to be verified for each project.
If your project comes up just a little short, consider supplementing some of your potable water use with graywater or rainwater, or installing composting toiletsComposting (or Nonwater) toilet systems are dry plumbing fixtures and fittings that contain and treat human waste via microbiological processes..
Onsite wastewater treatment has a number of environmental and educational benefits, but treating to tertiary standards can be challenging for some projects, especially if they have limited space.
Treating to tertiary standards involves extra filtration or biological activity to remove nutrient pollutants such as nitrogen and phosphorus, and it may also involve disinfection. Treating wastewater to this level goes beyond code in most places. Consider technologies that are passive or low-tech in order to minimize operation and maintenance costs.
The WEc2 calculations are based on the annual generation of blackwaterBlackwater is wastewater containing urine or fecal matter that should be discharged to the sanitary drainage system of the building or premises in accordance with the International Plumbing Code, or sewage, from flush fixtures as documented in WEp1. Note that the scope is not the same as WEp1, which includes both flush and flow fixtures.
Yes, per LEED InterpretationLEED Interpretations are official answers to technical inquiries about implementing LEED on a project. They help people understand how their projects can meet LEED requirements and provide clarity on existing options. LEED Interpretations are to be used by any project certifying under an applicable rating system. All project teams are required to adhere to all LEED Interpretations posted before their registration date. This also applies to other addenda. Adherence to rulings posted after a project registers is optional, but strongly encouraged. LEED Interpretations are published in a searchable database at usgbc.org. #10012 made on 05/09/2011, "projects may only count future infrastructure such as reclaimed water systems so long as they will be completed and functional within 1 year." Anything further out than one year may not be counted, however.
Check for local or state incentives for water conservation, which can make this credit more feasible. Rebates are common. Also, some municipalities offer treated wastewater to buildings, which may be used for toilet flushing (although in most places it is restricted to landscape use).
Check for codes that may limit your options or force you to obtain a variance. Plumbing codes often restrict or regulate the following water-saving technologies:
Perform a water-balance study for the entire project in order to make an informed decision about where to focus your water-saving efforts. Survey your project and site for all water sources—stormwater, graywater, and onsite wastewater.
Calculating irrigation water use is not required for this credit; however, understanding how indoor water use compares to outdoor water use can help you gauge where to focus your reduction efforts for the greatest benefit. Some water-saving strategies address both indoor and outdoor water needs holistically. For example, if you treat your wastewater onsite, you can use the treated water to irrigate your landscape as well as to flush toilets. Doing so can contribute to either WEc1: Water Efficient Landscaping or WEp1 and WEc3: Water Use Reduction.
Establish goals for indoor and outdoor water and wastewater reduction. You may want to include those goals in the Owner’s Project Requirements for EAp1: Fundamental Commissioning and EAc3: Enhanced Commissioning.
Consider reducing potable wastewater use by 100%, or treating 100% of your wastewater onsite to tertiary standards, for an Exemplary Performance point.
Determine which option is best for your project:
Some municipalities requiring rainwater capture to reduce stormwater runoff; if this is the case in your area, consider reusing the rainwater for toilet flushing.
Reusing graywater or rainwater incurs additional costs and requires dual plumbing. If you use an under-sink graywater system that shunts the water directly from the sink to the toilet, this also involves additional cost but may be less expensive than a centralized, dual-plumbed system.
Onsite wastewater treatment costs vary widely. Treating to tertiary standards, as required by this credit, can cost significantly more than treating to secondary standards.
Determine if composting toilets or waterless urinals are appropriate for your project. While not common, waterless fixtures can go a long way toward achieving this credit. Composting toilets do affect programming and layout, however, so be sure to consider them early in the planning stages. However, projects often find that installing only a few composting toilets can help them to achieve this credit while offering a great educational asset.
Check with the local municipal wastewater department to see if reclaimed water is available as a source of non-potable water for toilet flushing. If it is available, this will contribute to compliance with Option 1.
Determine your project’s baseline case wastewater generation. This will help you develop your strategy for reduction.
When using the LEED Online credit forms, you need to complete the WEp1: Water Use Reduction—20% Reduction credit form first. Doing so automatically generates your baseline-case usage in WEc2. (See WEp1 for details on determining occupancy, usage, and FTE.)
Reducing your shower or sink flow rate will not help with credit compliance for WEc2 but, will help with WEp1 and WEc3. However, if your project is earning this credit through treating wastewater onsite, it is best to reduce the total quantity of water being treated. Therefore, a reduction in flow fixtures will minimize the total water needing treatment.
Begin developing your strategy for wastewater use reduction based on the option you’ve selected. Research low-flush fixtures, water reuse, and onsite treatment.
Well and pond water are not considered non-potable water for the purposes of this credit and must count as potable water—so you won’t get credit for substituting them for conventional water sources. Water types that do count as non-potable are: graywater (lavatory, sink, and shower water), rainwater, treated wastewater, air-conditioner condensate, reverse-osmosis reject, and sump-pump water.
Consider monitoring wastewater reduction in conjunction with EAc5: Measurement and Verification.
Consider installing permanent water metering for ongoing monitoring of the project’s water use. A submetering system can help operations staff detect problems early and facilitate future LEED-EBOM certification.
Select water-efficient flush fixtures and determine the percentage of reduction from fixtures alone.
Consider the different maintenance requirements for waterless fixtures. Waterless urinals and composting toilets require a different maintenance program from conventional fixtures.
Remember that this credit is based on EPAct 1992 and subsequent rulings of EPAct 2005, the 2006 Uniform Plumbing Code, and the International Plumbing Code. The baseline case for this credit includes these standards:
Track and record information on applicable fixtures, including the manufacturer, model number, and flush or flow rate. This will help you when filling out the LEED Online credit forms. Fill out the LEED Online form early in design simply as a draft to determine if you are meeting the requirement.
Typically, a dual-flush toilet—with the heavy-flow at 1.6 GPF and low-flow at 0.8 GPF—does not meet the credit requirements. However, a 1.0 GPF ultra-low-flow toilet or a 1.28/0.8 GPF dual-flush toilet—in conjunction with waterless or pint urinals—will meet the credit requirements, and you can avoid using non-potable water. For occupancies that do not use urinals, such as pre-kindergarten or elementary schools, you may not be able to meet this credit through the use of fixtures alone and you’ll find that you have to include water reuse in your water reduction stragey.
If you cannot meet the credit through the use of fixtures alone, determine how much non-potable water you need to use in order to comply.
Review your water balance study and determine what water reuse would be most appropriate for your project. If you have gym showers, it might be best to treat and reuse graywater from laundry or shower facilities. If the building is located in a rainy climate, you can capture and reuse rainwater.
If needed, size graywater and rainwater systems to satisfy the credit requirements. Sizing these systems can be more complicated than you might initially think. It’s best to involve a civil engineer or someone familiar with these systems.
Untreated rainwater and graywater may corrode plumbing systems or lead to biological growth. You should plan for water treatment and filtration, or use corrosion-resistant materials. All graywater plumbing and storage must be separate from regular sewage plumbing.
If you will be using graywater, rainwater, or treated wastewater, you’ll need dual plumbing for interior water fixtures. Communicate this need to your civil and plumbing engineers. You should also discuss any location and structural issues if your project is going to have a rainwater cistern—sometimes they take up more space than anticipated.
A dual plumbing system and rainwater or graywater reuse are likely to add upfront costs but the owner may recoup some of that cost in reduced water and sewer charges. However, most current utility rates for water and sewer are too low to justify these systems on a cost basis alone.
Typically, dual-flush and composting toilets have a higher cost over conventional fixtures but reduce water charges. Some ultra-low-flow toilets have a cost premium as well, but it is typically not as significant as a dual-flush or composting toilet.
Compare the baseline and design case water budgets to determine the water reduction percentage for your project. The LEED Online credit form has a built-in calculator to facilitate this calculation. Repeat this process until selection of water fixtures and strategies is finalized and your project’s water reduction goals have been met.
Even if you are attempting Option 2, you will want to select water-efficient fixtures, which minimize the quantity of wastewater treated onsite. To accomplish this, target the most consumptive fixtures to achieve the greatest water reduction, but keep in mind the very different maintenance requirements for waterless fixtures. See WEp1 and WEc3: Water Use Reduction for more information. Also, review the Option 1 steps of this credit.
Determine what type of onsite wastewater treatment is most appropriate for your project. Typical septic-tank-and-leachfield systems used in many rural areas where there are no sewer systems do not treat water to tertiary standards so they can’t be used to earn this credit.
Verify that your onsite wastewater treatment system is capable of treating the wastewater to tertiary standards. State governments determine exactly what constitutes “tertiary treatment” based on allowable remaining levels of certain nutrients and organisms. Your civil engineer will need to be in charge of this determination.
Determine how treated wastewater will be used onsite. It must either be reused, such as for toilet flushing or irrigation, or must be infiltrated onsite.
Treating wastewater simply for sewage conveyance can be expensive, so make the most of tertiary-treated wastewater by using it for as many non-potable water applications as possible—irrigation, toilet flushing, and cooling tower makeup water.
While the capital cost of wastewater treatment is a significant deciding factor, seek technologies or strategies that have low maintenance requirements to keep operations and maintenance costs low. Alarm systems for malfunctioning wastewater treatment systems can be expensive, be sure to research this.
Depending on the technology used and state or local regulations, tertiary wastewater treatment may require contracting with an outside company for operations and maintenance. When researching treatment technologies, inquire about maintenance procedures and requirements.
Include any low-flow or waterless fixtures, water reuse systems, or onsite wastewater treatment systems in your construction and design development documentation.
Be certain that the contractors reviewing construction documents understand the purpose of any dual-plumbing system in the plans. Misunderstandings about plumbing can lead to costly and unsanitary mistakes—like cross-connection with potable water lines.
Consider including signage for water reduction strategies that may require special instructions for use. These may include: occupant signage for operating dual-flush toilets, waterless urinals and composting toilets, and for indicating non-potable water—and operational signage for distinguishing the pipes that carry reused water. Purple piping is commonly used for reclaimed water and, more recently, for recycled graywater.
If reusing graywater or rainwater, or treating wastewater onsite, ensure that the key system components, such as treatment and collection facilities, are not eliminated during value engineering.
Fill out the LEED Online credit form. The total calculated flush-fixture water-use for the baseline and design cases will be automatically generated once the WEp1 credit form is filled out. You will need to provide information on annual reused water amount and, and if necessary, plumbing drawings or calculations illustrating that your non-potable water systems are capable of supporting the quantities determined.
Fill out the LEED Online credit form. The total calculated flush-fixture water-use for the baseline and design cases will be automatically generated once the WEp1 credit form is filled out. You will need to provide information on the blackwater source (toilet or urinal), annual quantity treated, annual quantity infiltrated onsite, annual quantity reused onsite, and plumbing drawings or other documents that detail information about the onsite treatment, infiltration, and reuse capabilities of your project.
Be sure you’ve included startup of a wastewater treatment system in contract documents and scope of services. You may want the commissioning agent to look at the wastewater treatment system too.
The contractor needs to verify that the correct fixtures have been purchased and that applicable water reuse or treatment systems have been installed properly.
Be sure to use purple pipes or otherwise clearly label supply pipes carrying non-potable water. This practice avoids inadvertent cross-connection with potable water lines and provides educational value.
When using an innovative wastewater treatment system unfamiliar to local regulatory officials, include them in regular construction inspections. This often helps to ease acceptance, and avoid unexpected objections or problems.
Apply for water-reduction incentives and rebates through your municipal water authorities.
Provide building managers with manuals for all water fixtures, water reuse technologies, onsite water treatment systems, and unconventional products used.
If a submetering or ongoing monitoring system is in place, be sure to track and record monthly use. This can help detect problems, contribute to a comprehensive M&V plan, and help with LEED-EBOM certification.
Train cleaning and operations staff to maintain atypical fixtures such as waterless urinals, composting toilets, and graywater collection and rainwater catchment systems.
Some wastewater treatment systems require trained personnel to operate them.
Excerpted from LEED 2009 for Schools New Construction and Major Renovations
To reduce wastewater generation and potable waterPotable water meets or exceeds EPA's drinking water quality standards and is approved for human consumption by the state or local authorities having jurisdiction; it may be supplied from wells or municipal water systems. demand while increasing the local aquifer recharge.
Reduce potable waterPotable water meets or exceeds EPA's drinking water quality standards and is approved for human consumption by the state or local authorities having jurisdiction; it may be supplied from wells or municipal water systems. use for building sewage conveyance by 50% through the use of water-conserving fixtures (e.g., water closets, urinals) or nonpotable waterNonpotable water: does not meet EPA's drinking water quality standards and is not approved for human consumption by the state or local authorities having jurisdiction. Water that is unsafe or unpalatable to drink because it contains pollutants, contaminants, minerals, or infective agents. (e.g., captured rainwater, recycled graywaterGraywater is untreated household waste water which has not come into contact with toilet waste. Graywater typically includes used water from bathtubs, showers, bathroom wash basins, and water from clothes-washer and laundry tubs, though definitions may vary. Some states and local authorities also allow kitchen sink wastewater to be included in graywater. Project teams should comply with the graywater definition established by the authority having jurisdiction in the project area., on-site or municipally treated wastewater).
Treat 50% of wastewater on-site to tertiary standards. Treated water must be infiltrated or used on-site.
Specify high-efficiency fixtures and dry fixtures (e.g., composting toilet systems, nonwater-using urinals) to reduce wastewater volumes. Consider reusing stormwater or graywaterGraywater is untreated household waste water which has not come into contact with toilet waste. Graywater typically includes used water from bathtubs, showers, bathroom wash basins, and water from clothes-washer and laundry tubs, though definitions may vary. Some states and local authorities also allow kitchen sink wastewater to be included in graywater. Project teams should comply with the graywater definition established by the authority having jurisdiction in the project area. for sewage conveyance or on-site mechanical and/or natural wastewater treatment systems. Options for on-site wastewater treatment include packaged biological nutrient removal systems, constructed wetlands and high-efficiency filtration systems.
This website offers a plumber’s perspective on many of the major toilets used in commercial and residential applications.
This site provides two reports on independent test results for a variety of toilets’ flush performance and reliability.
ARCSA was founded to promote rainwater catchment systems in the United States. The ARCSA website provides regional resources, suppliers, and membership information, and publications such as the Texas Guide to Rainwater Harvesting.
This manual provides a focused and performance-based approach to on-site wastewater treatment and system management. It also includes information on a variety of on-site sewage treatment options.
WaterSense is a U.S. Environmental Protection Agency program designed to encourage water efficiency in the United States through the use of a special label on consumer products. It was launched in 2006. The WaterSense website offers information on certified products, and other water conservation information from its partners.
The LEED Online credit form offers a useful calculator for this credit that we recommend. The scenarios shown in these sample calculations show how this credit can play out with percentage savings based on fixture selection alone.
The following links take you to the public, informational versions of the dynamic LEED Online forms for each Schools-2009 WE credit. You'll need to fill out the live versions of these forms on LEED Online for each credit you hope to earn.
Version 4 forms (newest):
Version 3 forms:
These links are posted by LEEDuser with USGBC's permission. USGBC has certain usage restrictions on these forms; for more information, visit LEED Online and click "Sample Forms Download."
Documentation for this credit can be part of a Design Phase submittal.
I heard that there may be issues with very low-water WCs, such as the 2-4 liters per flush – i.e. in the sense that you would need to flush it twice to get the effect needed.
1- Does this fact hinder their reliability? Is there any recommended measures to reduce the problem with such WCs?
2- What would be the lowest reasonable low-flush WCs we should aim at specifying without running into this problem?
3- Is there any index other than gallons-per-flush that may help in deciding whether it is recommended to use low-water WCs?
A number of factors affect the reliability, from the manufacturer, the design of the fixture, flushing method, and how long fixtures have been sold at the particular flow rate, so it’s difficult to recommend a lowest flush volume.
For commercial flush-valve fixtures (those without their own tank) we've seen issues when the porcelain bowl is made by one company, and the plumbing valves are made by a different company. Better results can result from using the same company for both bowl and valve. The first round of models made for the lower flow rates tend to have more problems than the second generation, when problems get figured out.
In tank-style toilets, the factors than can affect performance include the diameter of the trapway, whether the toilet uses siphonic action or “wash down” method, (which is more common in Europe), and whether there is pressure assistance or power assistance to aid the flushing action.
In the USA, the low range of flush volumes is 1.1 to 1.28 gallons per flush, or 4.2 to 4.8 liters per flush, but others may have more experience with the 2-4 liter range you mention in other countries. For ratings on the Maximum Performance (MaP) testing of many residential and commercial fixtures in the US see, http://www.cuwcc.org/MaPTesting.aspx .
I would also check the "GreenSpec Products" shown in the sidebar to the right on this page. (Clicking through to view detail on any of the products listed will require a separate membership to GreenSpec, which is published by BuildingGreen, also the makers of LEEDuser.)
GreenSpec has a great screening of products that not only perform well in terms of water efficiency, but they also flush the **** down the toilet!
Tips and screenshots on LEED Online documentation.
Do you know which LEED credits have the most LEED Interpretations and addenda, and which have none? The Missing Manual does. Check here first to see where you need to update yourself, and share the link with your team.
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