Part VI. Performance Requirements
12VAC5-635-290. Performance requirements; general.
A. The owner shall ensure that a rainwater harvesting system operates in compliance with the following performance requirements:
1. For a rainwater harvesting system designed to supply water for Tier 2, 3, or 4 end use, the owner or operator shall conduct treatment using a combination of filtration and disinfection technologies to the minimum standards described in 12VAC5-635-310.
2. If a rainwater harvesting system provides water for multiple end uses and treatment is not separated by end use, the highest treatment standard shall apply for all uses.
3. If a rainwater harvesting system provides water for multiple end uses and treatment is separated by end use, connection to distribution for each end use shall comply with the USBC.
B. The designer of a rainwater harvesting system shall consider the following factors:
1. The anticipated harvested rainwater characteristics and flow, including consideration of extremes of precipitation patterns. Excess precipitation not captured for storage shall be discharged as runoff. Insufficient precipitation that does not allow a rainwater harvesting system permitted for Tier 2, 3, or 4 end use to maintain sufficient storage shall be managed as described in 12VAC5-635-300.
2. The prevention of potentially harmful precipitation, such as that which could incorporate particulates from fires, from being captured and contained in the system.
3. The selection and sizing of components of sufficient structural integrity to minimize the potential of physical harm to humans and animals.
4. The sizing of the system in recognition of both the available collection area and number of users of the harvested rainwater. The designer of a Tier 4 rainwater harvesting system shall size the system pursuant to the following criteria:
a. A demand of 100 gallons per bedroom per day for residential systems using either a private well or public water for continuity of water supply pursuant to 12VAC5-635-300 C.
b. A demand of 150 gallons per bedroom per day for residential systems using hauled water for continuity of water supply pursuant to 12VAC5-635-300 C.
c. For nonresidential systems, the designer shall provide calculations supporting the anticipated demand.
Statutory Authority
§§ 32.1-12 and 32.1-248.2 of the Code of Virginia.
Historical Notes
Derived from Virginia Register Volume 41, Issue 5, eff. November 20, 2024.
12VAC5-635-300. Continuity of water supply.
A. "Continuity of water supply" means that a continuous supply of water can be provided to a distribution system supplied by a rainwater harvesting system in the event of insufficient precipitation or other circumstances affecting the supply of harvested rainwater.
B. If a rainwater harvesting system serves as a secondary supply for a distribution system and the primary supply is a waterworks, the rainwater harvesting system shall be an auxiliary water system pursuant to the requirements of the USBC and 12VAC5-590.
C. If a rainwater harvesting system serves as a primary supply for a distribution system for a Tier 2, 3, or 4 end use, the owner shall provide a secondary water supply by a waterworks, a Class III private well, or commercially hauled water meeting pure water standards.
D. The owner shall supply a secondary water supply from a waterworks or private well by a means to refill the water storage unit or a bypass that provides water directly to the distribution system.
E. The owner may only use commercially hauled water to refill a water storage unit prior to filtration and treatment.
F. When water from a secondary water supply is added to a water storage unit, the owner shall ensure that the water is introduced through a reverse pressure principle backflow device or an air gap pursuant to the USBC.
Statutory Authority
§§ 32.1-12 and 32.1-248.2 of the Code of Virginia.
Historical Notes
Derived from Virginia Register Volume 41, Issue 5, eff. November 20, 2024.
12VAC5-635-310. Water quality standards.
A. The owner shall perform initial water quality testing before the use of water from the rainwater harvesting system and subsequent water quality sampling and testing consistent with the schedule in 12VAC5-635-320 and in accordance with the operation and maintenance manual requirements of this chapter.
B. The owner shall:
1. Flush the system at least once with treated harvested rainwater before water quality testing and discharge the flush water as wastewater;
2. Collect samples for water quality testing from a point-of-use outlet intended for regular use, such as a kitchen sink;
3. Collect first draw samples of one liter for lead testing;
4. Ensure that water quality samples are analyzed by a laboratory certified by the Division of Consolidated Laboratory Services for drinking water samples; and
5. Ensure that the water is tested in accordance with the minimum performance criteria in Tables 3 and 4 and, at minimum, for total coliform or E. coli present, total nitrate and nitrite content, pH, and lead content.
TABLE 3 Minimum Performance Requirements | |||||||
Application | Log Reduction Target | ||||||
End Use Tier | Category | Potential for Human Contact | Example Use | Viruses | Bacteria | Protozoa | pH |
1 | Nonpotable | Low | Trap primers Spray irrigation (restricted access) Surface and subsurface irrigation Ice rinks | 0* | 0 | 0 | N/A |
2 | Nonpotable | Medium | Toilet and urinal flushing Clothes washing HVAC evaporative cooling Rooftop thermal cooling | 0* | 2 log | 2 log | N/A |
3 | Nonpotable | High | Hose bibs Pressure washing Decorative fountains Vehicle washing Spray irrigation (nonrestricted access) Firefighting or protection and fire suppression | 0* | 3 log | 3 log | N/A |
4 | Potable | High | Human consumption | 0* | 6 log | 6 log | 7-10.5 |
* It is unlikely that human infectious viruses are present in harvested rainwater. However, if underground water storage tanks are used where there is a potential for sewage contamination or surface water infiltration, a 4-log reduction for viruses shall be required. | |||||||
TABLE 4 Requirements for Tier 4 Potable Water | |
Design Standards | |
Filtration | 5 µm |
Disinfection | 40 mi/cm2 and labeled certified to Class A of NSF/ANSI 55 |
Water Quality Parameters | |
Turbidity | <0.3 NTU |
Lead | <15 µg/L |
Nitrates | <10 µg/L |
C. Before the commissioner issues an operation permit for a rainwater harvesting system intended for Tier 4 use, the owner must document that the treated harvested rainwater has been tested and meets primary U.S. Environmental Protection Agency drinking water standards (inorganic), the tests listed in subdivision B 5 of this section, and the tests listed in Table 4. If a primary drinking water standard or design standard is exceeded, the owner may provide additional treatment to address the exceedance and shall resample the treated harvest rainwater to ensure compliance with this subsection. Testing for inorganic primary drinking water standards shall not be required for subsequent monitoring unless specified in the operation and maintenance manual prepared pursuant to 12VAC5-635-350.
D. The owner shall conduct water quality sampling and monitoring in accordance with the procedures approved under 40 CFR Part 136 or alternative methods approved by the department, unless other procedures have been specified in this chapter.
E. The designer shall identify the rainwater harvesting system's water quality sampling points, which shall be downstream of the treatment steps and upstream of the point of use. If total residual chlorine is used to measure compliance in a system using chlorine disinfection, the sampling point must be downstream of the chlorine contact tank. If ultraviolet (UV) disinfection is used, the owner may not use water samples collected upstream of UV disinfection units for dosage adjustment for the purposes of water quality testing pursuant to this section.
Statutory Authority
§§ 32.1-12 and 32.1-248.2 of the Code of Virginia.
Historical Notes
Derived from Virginia Register Volume 41, Issue 5, eff. November 20, 2024.