Correspondence (10) State Of Oregon
Building Codes Division
Alternate Method Ruling No. OPSC 08-03
APPROVAL OF RAINWATER HARVESTING SYSTEMS AS A STATEWIDE
ALTERNATE METHOD OF PROVIDING WATER FOR NON - POTABLE USES
Statewide Alternate Methods are approved by the Division administrator in consultation with
the appropriate advisory board. The advisory board 's review is limited to the technical and
scientific merits of the proposal. In addition:
• building officials shall approve the use of any material, design or method of construction
addressed in a statewide alternate method,
• the decision to use a statewide alternate method is at the discretion of the designer,
• statewide alternate methods do not limit the authority of the building official to consider
other proposed alternate methods encompassing the same subject matter
Initiated By: The Building Codes Division
APPLICABLE CODE SECTION:
None
BACKGROUND:
The State of Oregon approved scientific and technical facts for limited rainwater harvesting
systems for potable uses, alternate method ruling No. OPSC 08 -01. Based on numerous
conversations with industry and developers, the division has created a proposed supplemental
statewide alternate method to address typical non - potable uses for rainwater. These include
irrigation/garden, hose bibbs, toilets, urinals, clothes washing and heating, ventilation, and air
conditioning (HVAC) make -up water supplies. These uses require less treatment and limited or
no disinfection. This alternate method addresses uses applicable to residential and commercial
installations.
Rainwater harvesting under this method may not be used for apartments or commercial buildings
used for childcare or schools. Rainwater harvesting systems used in commercial or residential
applications that only provide irrigation are exempt from this ruling and the plumbing code.
Rainwater under this alternate method may only be collected from roofs.
Rainwater harvesting is currently used in many other states and countries. Rainwater harvesting
is being done in Ohio, Texas, Arizona, New Mexico, Hawaii, Virgin Islands, Germany,
Australia, India and many other locations around the world. Many of these locations rely on a
variety of national construction standards.
PROCEDURAL HISTORY:
The division initiated this alternate method ruling as a means of addressing sustainability in
Oregon. On June 20, 2008, the Oregon State Plumbing Board approved scientific and technical
facts relating to the statewide alternate method No. 08 -3, rainwater harvesting for commercial
potable uses. This alternate method addresses additional rainwater harvesting for non - potable
uses only.
TECHNICAL DISCUSSION:
Under Oregon law, when the division considers making an alternate method ruling on a
method of construction, it must consider "standards and interpretations published by the body
that promulgates any nationally recognized model code adopted as a specialty code of this
state." ORS 455.060.
The International Association of Plumbing and Mechanical Officials (IAPMO) through its
Evaluative Services and in the text of the Uniform Plumbing Code, recognizes stormwater
harvesting management, including rooftop harvesting methods. However, because the current
model code does not specifically address rainwater this alternate method is necessary. Product
standards and approved materials are listed in Table 14 -1 of the Uniform Plumbing Code.
FINDINGS:
As approved by the Oregon State Plumbing Board, the following scientific and technical facts
apply to rainwater harvesting system for non - potable uses as an alternate method:
• The statewide alternate method ruling OPSC 08 -03 provisions address rainwater
roof collection and catchment areas in terms of materials and slopes.
• The statewide alternate method ruling OPSC 08 -03 provisions address rain leader
piping, first -flush diverter systems, storage tanks and pumps.
• Approved rainwater harvesting systems shall be installed as per the statewide
plumbing code, the attached ruling, American National Standards Institute
(ANSI) accredited product listings and to the manufacturer's installation
instructions.
• The non - potable statewide alternate method ruling OPSC 08 -03 is limited to roof
top collection systems in both residential and commercial applications with the
exception of apartment buildings and commercial structures containing childcare
and schools.
• Rainwater harvesting is currently used in many other states and countries,
including California, Washington, Ohio, Texas, Arizona, New Mexico, Hawaii,
Virgin Islands, Germany, Australia, India and many other locations around the
world.
SCOPE OF RULING:
Following consideration of the scientific and technical facts approved by the Oregon State
Plumbing Board and the Residential Structures Board, the division rules that rainwater
harvesting systems for irrigation/gardens, hose bibbs, toilets, urinals, clothes washing and make-
up water for HVAC systems shall be allowed. The division has determined that rainwater
harvested only for commercial or residential gardens or irrigation are exempted from the
requirements of this alternate method ruling except #11, and must simply be designed to not
interact with the potable water supply, the building sanitary sewer or septic system, or cause
damage to property or erosion. This ruling does not recognize installation in apartments or
commercial buildings used for childcare or schools, at this time. The proper system design,
maintenance and use are the responsibility of the building owner.
1. Except as otherwise provided for in this alternate method, the provisions of the Oregon
plumbing code, where appropriate, shall be applicable to rainwater harvesting systems
for non - potable uses. The alternate use of rainwater harvesting systems for non - potable
uses are in addition to the other requirements of the Plumbing Code.
2. The following definitions apply to rainwater harvesting systems:
Catchment — Means only a roof surface used for the collection of rainwater.
Downspout — The rain leader from the roof to the rainwater storage vessel.
First -Flush Diverters — A device which collects the initial rainwater from a catchment
during a rain event and disposes of the potentially contaminated water.
Leader — An exterior vertical drainage pipe for conveying storm water from the roof or
gutter drains.
Non- Potable Water — Rainwater harvested for the purpose of supplying water to hose
bibbs, toilets, urinals, clothes washing irrigation/garden and HVAC make -up water.
Potable Water — Water that is satisfactory for drinking, culinary, and domestic purposes.
3. All piping and plumbing component materials used in the installation of a rainwater
harvesting system shall be as approved for the specific use in the Oregon plumbing code
or be listed by an ANSI accredited product certification program.
4. Collection roofing, gutters, piping, fittings, valves, screens, downspouts, leaders, flushing
devices, tanks and liners shall be approved for the intended use.
5. All surfaces, tanks and equipment shall be washed clean before they are put into service.
6. Materials used in rainwater harvesting systems shall be listed by an ANSI accredited
product certification program.
7. Harvested rainwater must be filtered or treated to an appropriate quality. No treatment is
necessary for irrigation/garden use only.
8. All piping in the system shall be easily recognizable. Harvested rainwater piping
downstream of the storage tank shall be marked by being purple in color, or being
marked clearly with purple tape or stripe, or being painted purple with compatible paint,
or being labeled at intervals of not more than five feet with the words NON - POTABLE
WATER.
9. Rain barrels may be used at downspouts for collection of water for irrigation only. Rain
barrels shall be screened with a fine mesh (.05 inch x .05 inch) to prevent mosquitoes
from entering. No plumbing permit is required for rain barrels.
10. Outlets and fixtures served with harvested rainwater shall be easily recognizable by color
or a symbol for non - potable water.
Universal Symbol for Non- Potable Water
1 1. No part of a private potable water system source, treatment system, plumbing system or
water served fixture shall be connected with any part of a public drinking water system
without appropriate backflow protection.
12. Rainwater shall only be collected from roof surfaces. Roof surfaces shall be constructed
of slate, metal, tile, concrete, fiberglass or other approved material.
13. Roof catchments shall be accessible, maintained clean and free from debris. Roof
catchment area shall be based upon the foot print of the roof and not the actual area of
the roof surface. The foot print area of the roof catchment shall be calculated by
measuring the outside dimension of the roof and multiplying length times width.
14. Gutters intended to capture rainwater for harvesting shall be the continuous or seamless
type and constructed of materials which are approved for their intended use. A gutter
shall be screened with an approved material over its entire opening to keep out leaves,
debris and other large contaminants or have a screened collection point. Gutter screens
shall not have an opening greater than one -half (1/2) inch (12 mm).
15. Gutters shall have a continuous grade with a minimum slope of one - sixteenth (1/16) inch
per foot to the outlet leader with no sags or flat portions where water will collect or stand.
Gutters shall be clean and maintained on a regular basis. Run off of wash water shall be
diverted from the storage tanks to a location which will not cause damage to property or
cause erosion.
16. Gutter outlets may be connected indirectly to the rain leader with a screened leaf
protected receptor inlet.
17. All piping from gutters to the storage tanks shall be continuously graded from the roof to
the tank. Piping shall have a continuous grade with a minimum slope of one - fourth (1/4)
inch (6 mm) per foot (300 mm) to the storage tank. Except for first -flush washers, no
section of piping shall be installed in a manner which will hold water and not drain
completely. Trapping of piping is prohibited.
18. Plastic piping shall be protected from UV radiation by a factory applied protective
coating or painted with a compatible latex paint. Piping and solvent cements shall be
approved for the intended use.
19. Metal rain leaders shall be seamless aluminum, galvanized steel or other approved
material.
20. Piping from down spouts to storage tanks shall be sized according to Table 11 -1 of the
plumbing code.
21. All rainwater harvesting systems shall have a first -flush diverter installed in a manner
which will divert the first flow of water from the catchment surface during each rain
event. Water drained from the first -flush diverter will be piped away from the storage
tank and terminate in a location which will not cause damage to property or erosion.
22. First -flush diverters shall be sized so that the minimum volume of the water diverted is at
least equal to ten (10) gallons (30.8L) per each rain event and be listed factory assemblies
or constructed of approved materials on site.
23. First -flush diverter vessels shall have a cleanout fitting in the bottom of the device. First -
flush diverters shall be provided with an automatic means of self - draining between rain
events.
24. Storage tanks may be constructed of fiberglass, polypropylene, metal, concrete,
ferrocement, wood or listed material. Storage tanks shall be opaque or painted to prohibit
algae growth. Polypropylene tanks shall not be painted.
25. Storage tanks shall be listed for use with water and be provided adequate access for
cleaning and maintenance purposes. Storage tanks which have been previously used for
other purposes are prohibited. Storage tanks must be completely covered and any vent or
other opening screened to prevent mosquito breeding. Covers must be sturdy and be
constructed in such a way that they will not allow water to pond or collect on the surface.
26. Storage tanks shall be as close to the catchment area as is practical and protected from
sunlight or other light source in an approved manner In areas where freezing
temperatures are frequent adequate provisions shall be made to protect the tank and
connected piping from freezing.
27. Storage tanks shall be provided with an overflow equal in size to the tank inlet.
Overflows shall be piped away from the tank and the water shall be disposed of in a
manner which will not cause damage to property or erosion. Overflow drains shall be
equipped with durable animal guards or screens. Connection of overflow piping to any
sanitary or storm/sanitary combined sewer piping is prohibited.
28. Above ground storage tanks shall be placed on a stable, level surface of sufficient
strength to accommodate the size and weight of a full tank.
29. Buried plastic storage tanks shall be reinforced and able to withstand the weight of the
surrounding fill and soil and full capacity of water. Concrete tanks which are above
ground or underground must be constructed to withstand the load of water capacity and
any other applicable structural forces.
30. Storage tanks shall be watertight and designed to withstand the structural loads required
for their size and shape. Tanks shall be vented when necessary. The vent shall turn
down and be equipped with a screen to prevent mosquitoes from entering.
31. Storage tanks shall not be connected directly to a public or community water supply
without proper backflow protection. Make up water to rainwater storage tanks, when
provided, may be made through a properly sized and constructed air gap as per Oregon
plumbing code Table 6 -3.
32. Pressure tanks and pumps shall be of an approved type listed, designed and intended for
water use. Pressure switches shall be set to provide a minimum residual water pressure
of fifteen (15) pounds per square inch (103.4 kPa) in the building but shall be set no
higher than eighty (80) pounds per square inch (552 kPa). Pressure tanks shall be of the
expandable diaphragm type and sized based upon the peak flow capacity of the pump.
33. Pumps shall be a minimum of Y2 horsepower or as specified by the manufacturer. A full
size check valve shall be installed between the storage tank and the pump inlet. Pump
inlet piping shall be a minimum of one (3/4) inch (20mm) or as specified by the
manufacturer. Pressure tanks shall be sized based upon the demand required for the
intended use. On -demand type of pump systems, which incorporate the pump, motor,
controller, check valve and pressure tank may be used.
34. Pumps shall be at an elevation which is as close as practical to the elevation of the
storage tank. Pumps shall be installed in a location which is adequately protected from
freezing, overheating or where other potential damage may result.
35. Water intake supply from storage tanks to pumps shall be from a floating submerged
intake pipe or equivalent.
•
36. A preliminary screening of all water shall be installed between the catchment and the
storage tank. The screen mesh shall not have an opening greater than (1/2) inch (12mm).
The screen should be washed clean of debris after each rain event. Storage tank
screening shall be fine enough to prevent mosquitoes from entering.
37. Initially storage tank water may be treated with chlorine laundry bleach (which does not
contain additives) by manually adding one (1) ounce (.0296 L) for every 200 gallons of
water in the tank.
38. Adequate filters shall be installed for the intended water use. Cartridge filter elements
must be replaced as recommended by the manufacturer.
CONCLUSION:
After considering the technical and scientific approval by the Oregon State Plumbing Board, the
division rules that rainwater harvesting systems for non - potable uses are acceptable as a
construction method, subject to • ted limitations, and Alternate Method Ruling OPSC 08 - 03 is
approved. /
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