ACCEPTABLE SUPPLY
Acceptable sources of water supply for both potable and non-potable needs include harvested rainwater and stormwater, groundwater, condensate from the air, surface water sources such as ponds, recycled process water, and greywater and black water (sewage), water collected on site and treated appropriately for reuse. The use of reclaimed water delivered by large-scale public treatment facilities is also allowed.
Closed-Loop Water Systems
Project water needs must be met, to the maximum extent possible, by a closed-loop system within the carrying capacity of the site’s natural water systems. Ideally this means all water used by the project comes from, and is returned to, the project site (see figure 6-1). For example, if the water supply is rainwater, there must be sufficient opportunities for evapotranspiration and infiltration to support the natural ecosystem. When water is returned to the aquifer after use, it must be reintroduced so that it does not compromise natural systems (e.g., treated and reintroduced at an appropriate temperature to avoid thermal pollution, etc.).
Project teams must research the current functions and capacity of natural water sources and systems, and ensure that the project as developed emulates the natural hydrologic state of the site prior to human development to the maximum extent possible.
Should the project team be unable to meet the project’s water demands solely using on-site water resources, they are permitted to connect to the municipal water supply for the remaining water required after maximizing both water use reduction and the use of all on-site water resources. In addition, all non-potable water demand must still be met by non-potable sources.
Affordable housing projects are not required to maximize the use of on-site water resources. Instead, affordable housing projects can rely solely on handprinting, after maximizing water use reduction, to offset their total water demand if they choose.
Groundwater
If the supply is groundwater (i.e., wells), the project team must show that the aquifer is being recharged with the same amount that is withdrawn on an annual basis, and that withdrawing water for the project does not produce any negative or irreversible consequences (e.g., saltwater intrusion, draining of fossil water). The groundwater recharge analysis must include at minimum, a calculation based on a 40-year rainfall record such as the modified Chaturvedi method., or use of the soil water balance method, showing that the groundwater withdrawal rate does not exceed the groundwater recharge rate.
ACCEPTABLE OUTFLOW MANAGEMENT
Project teams have three options for managing and treating the project’s greywater and sewage.
Option 1 – On-site Treatment
Greywater and sewage can be treated and managed on site. There are numerous technologies readily available for on-site treatment such as greywater treatment systems, Living Machine, composting toilets, membrane bioreactors, constructed wetlands, treatment lagoons, and other forms of biologically based or mechanically based treatment trains. In addition, a septic system is an acceptable on-site strategy if the resulting effluent is designated for beneficial reuse. In some cases, a septic system may be sufficient to accept all greywater and sewage discharge. The prohibition on chlorine for water treatment also applies to septic systems.
Option 2 – Municipal Connection
An operational connection to the municipal sanitary sewer for greywater and/or sewage treatment and disposal is permitted, when the municipal system meets the following conditions:
• Uses a biologically based treatment process with no Red List chemicals used for treatment.
• Is located within the same watershed as the project.
• Captures nutrients from the treated water, including phosphorus, nitrogen, and biosolids.
• Treats water to tertiary levels and returns water in a balanced way to the same watershed for use.
In order to use a municipal connection, the project team must show that their contribution to the municipal system is not stressing the existing system, and that the project’s energy production produces sufficient energy to offset both a prorated amount of energy (i.e., kWh per gallon) from the plant treatment system, and also all pumping energy required to move the project’s sewage from the project to the treatment facility.
Option 3 – Handprinting
The project team may connect to a sanitary sewer system that does not meet the above criteria by handprinting that impact. In order to use this pathway, the project team must meter the amount of sewage sent to the municipal system and offset at least the same amount by investing in efficiency measures for another property served by the same municipal system, such that the total amount of sewage sent to the municipal system by both projects combined remains the same or is less after the LBC project has been built.
Figure 6-2 Water System Flow Chart. There are several compliant pathways by which a project team might connect to the municipal drinking water, reclaimed non-potable water, or sewage systems. This flow chart displays which project types and uses are eligible to connect, and the requirements to do so.BIOSOLIDS AND LEACHATE DISPOSAL
If the project team is treating sewage on site, they must develop a plan for the biosolids (solids) and leachate (liquids) that are produced as a result of the treatment process. Biosolids are created in the process of sewage treatment, both at a municipal and site scale.
Though rich in nutrients, these resources are often regarded as public health risks in disposal and can be wasted if there is no approval or plan for reuse. If a jurisdiction does not allow on-site usage of the biosolids as a soil amendment, it is permissible to work with a hauler to periodically remove the biosolids for off-site treatment and use. The off-site treatment must be within approximately 100 miles (160 km) of the project site, and the biosolids must be used beneficially.
EQUIPMENT FAILURE
In an instance of brief (e.g., up to 4-week) equipment failure, the 12-month performance period to demonstrate compliance with this Imperative does not need to be reset. The performance period may be stopped and restarted once the equipment is functioning properly, as long as performance data shows the system could have accommodated the volume and flow during the missing weeks.
FIT-FOR-PURPOSE WATER
Project teams are encouraged to use fit-for-purpose water —water that has had the minimum treatment necessary for the intended use—to minimize the resources used for treatment. However, use of water treated beyond the minimum is allowed to avoid requiring multiple treatment systems.
INITIAL WATER PURCHASE
An initial one-time water purchase of non-project-sourced potable water to fill cisterns is allowed.
METERING
The project must demonstrate at the time of certification that it has minimized, or met 100 percent of, its water demand through site-sourced water for a continuous 12-month performance period. The building must be at least 85 percent occupied at the start of the performance period, and the metered data must be adjusted appropriately to show that if/when 100 percent occupied, the project could still meet the water demand. Adequate water metering and tracking systems are required to show compliance. At a minimum, monthly readings must be recorded documenting the project’s actual water use (gal/month) as well as quantity from each supply source, including:
- Harvested rainwater
- Groundwater and/or surface water
- Condensate
- On-site reclaimed greywater and sewage
- Municipally provided reclaimed water
- Municipally provided potable water (when allowed)
Sub-metering by end use, such as for sinks, showers, mechanical systems, etc., is not required, but is good practice for troubleshooting any issues that may arise with a project’s water systems.
NON-POTABLE USES
For the purposes of this Imperative, the following end uses are considered non-potable, and the project team is required to meet those demands with non-potable water.
Non-potable Water Demands:
- Toilet and urinal flushing
- Landscape irrigation (see Irrigation Clarifications for guidance on Interior Landscapes)
- Cooling tower makeup supply
- Laundry
- Miscellaneous processes (e.g., equipment washing, dust prevention, etc.)
PERFORMANCE PERIOD
Please see Performance Period guidance, which applies to both water and energy, under Imperative I07, Energy and Carbon Reductions.
Treatment
Where a project team has met the criteria for fully occupied with less than 100% occupancy, the team must provide an extrapolation calculation to demonstrate that the treatment system has the capacity to treat the volume that would be expected at 100% capacity.
RESILIENCY STRATEGY
The project team is required to provide enough drinking water for regular building occupants for one week, in the case of a disaster. For the purposes of this Imperative, the requirement is one gallon per full time equivalent occupant per day.
Project teams are permitted to meet this requirement using non-potable water stored on site, if they provide at least one means of treating it to potable standards without use of municipal power, such as hand filters or iodine tablets. Project teams may count water stored in detention ponds, cisterns, or water heaters if there is a reasonable strategy and means to access and purify that water to potable standards when needed.
THE RED LIST AND WATER SYSTEMS
A number of common water system materials, such as piping, roofing, and UV disinfection lamps contain materials that are on the Living Building Challenge Red List. In some cases, there are temporary exceptions to allow the use of these materials when code or market limitations demand. Project teams pursuing both the LBC Water Petal and Materials Petal should see the LBC 4.0 Materials Petal Handbook for further information.
Piping Materials
Polyvinyl chloride (PVC) piping is commonly used for building water systems and is prohibited for projects pursuing the Materials Petal under Imperative 13, Red List, except in very limited circumstances defined through Exceptions (see I13 Exceptions). There are a wide range of alternative products that can be used in lieu of PVC piping such as HDPE (high-density polyethylene), polypropylene, PEX (cross-linked polyethylene), vitrified clay, concrete, ABS, copper, steel, and iron.
TREATMENT WITHOUT CHEMICALS
Water supply for the building, including recycled water, must be treated appropriately for its intended use without the use of harmful chemicals. Chlorine (Cl), calcium hypochlorite (Ca(ClO)2) and sodium hypochlorite (NaClO) for water purification are prohibited in projects pursuing this Imperative. These chemicals are all deemed to be possible carcinogenic, mutagenic, reprotoxic, and/or respiratory toxins by the US EPA and/or European Commission agencies.
Calcite (CaCO3), soda ash (Na2CO3), or caustic soda (NaOH) are acceptable additives to rainwater harvesting systems for pH buffering to prevent corrosion of metal piping materials and fixtures.
Ultraviolet disinfection (UV) is allowed. It should be noted, however, that UV disinfection lamps typically contain mercury, an item that requires the use of Exception RL-015, Mercury in UV Disinfection Lamps to comply with Imperative 13, Red List.
