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Legal and installation requirements for backflow protection

Technical information about how and where to install backflow prevention assemblies.

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Legal requirements

The Oregon Health Authority (OHA) Cross-Connection Control Requirements are the minimum requirements that a public water provider must adhere to when requiring backflow prevention assemblies be installed. The requirements on this page and Title 21—City Water Code require property owners to install backflow assemblies to protect the public drinking water supply. If you refuse to install, test and/or maintain a State or City-required backflow assembly, your water service may be terminated without further notice.

State rules and City Codes require you to:

  • install a backflow prevention assembly if there's an existing or potential cross-connection on your premises
  • test your assembly once per year
  • immediately have your assembly cleaned, repaired or replaced if not working properly
  • call the Water Bureau at 503-823-7480 before removing, replacing, or moving your assembly. If you want to remove your assembly, a Water Bureau Water Quality Inspector must verify that your premises no longer poses a backflow risk.

Backflow Assembly Installation Requirements 

  1. Premises-Isolation assemblies (those that directly protect the public water supply) must be installed on private property at the property line (service connection/point-of-delivery) on the centerline of the city water service, as it runs perpendicular from the right-of-way (R.O.W.).  Installations must be compliant with all applicable criteria stated herein. The supply side of premises-isolation assemblies must be plumbed with potable water piping and fittings meeting current NSF/ANSI standards for lead content. Premises-Isolation assemblies installed in buildings that extend beneath the R.O.W. must be installed at the riser/supply pipe where the water service enters the open space (determined by water service depth at the R.O.W.) or from the water meter vault and be compliant with all other applicable installation criteria stated herein. On a case-by-case basis with prior Water Bureau approval and provided there are no applicable Oregon Administrative Rules (OAR) dictating otherwise, a domestic Premises–Isolation backflow assembly may be installed at the riser/supply pipe prior to any piping branches and/or run of exposed piping in the plumbing system as opposed to immediately at the service connection/point-of-delivery to the premises (as defined in the OAR).  Point-of-Use assemblies (those installed on piping branches, i.e. irrigation systems, process water, etc.) must be installed on private property in conformance with the local plumbing code. Only approved Double Check Valve and Reduced Pressure Type backflow assemblies, in an approved configuration may be used as premises-isolation backflow protection. State and/or City required premises-isolation backflow protection is a condition of water service and/or continued service where an existing service requires premises-isolation protection.  Premises-Isolation assemblies must not be removed, replaced or relocated without first contacting the Water Bureau Water Quality Inspection group.

Backflow assemblies installed on water services that enter buildings with subgrade floors must conform to the following:

  • Enter a building perpendicular to the centerline of the city water service and at an elevation as determined by the depth of the city water service at the R.O.W.
  • Services entering at an elevation greater than 10-feet above-finished-floor (AFF) will require a permanent platform be installed.  The platform will need to provide for 6-feet of vertical headroom and the backflow assembly will need to be placed at an elevation that will accommodate 36” of vertical clearance above the assembly body.  Platforms must be engineered to comply with all applicable Oregon OSHA requirements and be detailed on all drawings submitted for review and permitting through City of Portland Bureau of Development Services (BDS).
  • Services entering at an elevation less that 10-feet will require that the backflow assembly be placed at 5-feet AFF, measured to top of assembly body.
  • If water service enters a building at an elevation (determined by the depth of city water service at the R.O.W.) between one and 5-feet AFF, the assembly must be installed at water service entrance elevation.

If water service enters a building from below grade (slab-on-grade) or at an elevation less than 1-foot above finished floor (AFF), the assembly is to be raised to 1-foot AFF (measured to the lowest part of the assembly).  Premises isolation assemblies approved to be installed inside buildings or structures must be installed at the water supply riser/supply pipe.  The riser/supply pipe must be installed 12” from the foundation wall to the centerline of pipe on the centerline of the city water service as it runs perpendicular from the R.O.W.  Foundations, footings, slabs and/or walls must be sleeved or core-drilled to accommodate code compliant riser/supply pipe entrance locations. 

  1. The installation of a backflow assembly may alter system operating pressure, flow and/or influence other hydraulic functions.  Additionally, thermal expansion may result from the installation of a backflow assembly.  The water user/installer is responsible for ensuring system operating requirements can be met 
  1. Retrofit/Replacement backflow assembly installations must meet current State and City installation requirements. 
  1. Backflow assemblies must be protected from severe environmental conditions.  Only commercially manufactured prefabricated insulated outdoor enclosures will be approved.  Drawings must be submitted and approved by Water Quality Inspection prior to constructing an alternate type of enclosure.  All exposed piping inside enclosures must be insulated with commercially manufactured pipe insulation or a heat source must be provided. 
  1. Premises-isolation backflow assemblies must be those approved by University of Southern California Foundation for Cross-Connection Control and Hydraulic Research (USC) and the Oregon Health Authority (OHA).
  1. Premises-isolation installations must meet minimum application and installation requirements listed in OAR 333-061-0070 and 333-061-0071, respectively, and those of the Portland Water Bureau.
  1. Only assemblies approved by USC and OHA may be installed vertically.
  1. In addition to City Code Title 21 and Title 28, OAR 333-061-0070, Section 14, will apply to all existing premises-isolation backflow assembly installations.  Required permits must be obtained and associated fees be paid prior to installing a premises-isolation backflow assembly. 
  1. Assemblies must be readily accessible with adequate room for testing and maintenance: 
  • Assemblies 2 inches and smaller, located in below grade vaults (excludes DCDA’s, see next bullet) must maintain at least 4 inch clearance on all sides and at both ends respectively. 
  • Assemblies larger than 2 inches (includes 2 inch DCDAs) must maintain at least 4 inch clearance on the backside, 3 inch at both ends, 12 inch underneath, 24 inch in front and 36 inch vertically above assembly body.  See required headroom clearances for vault, chamber/enclosure and basement installations.
  1. A minimum of a Double Check Valve Assembly (DCVA) for premises-isolation must be installed on water services: 
  • If the water meter is 2 inches or larger. 
  • If the service supplies properties where vending cart(s) are permitted. Where Frost-Free Drain-Back Yard Hydrants and/or Sanitary Yard Hydrants are used on the premises, RPBA protection must be provided. 
  • All services considered non-potable and do not pose a risk to health.
  • Existing services where water is being used for the sole purpose of facilitating temporary construction needs and does not pose a risk to health.
  • If the Water Bureau determines the backflow potential warrants and the use does not pose a risk to health. 
  1. Premises-Isolation assemblies installed at an elevation greater than 5-feet measured to top of assembly body AFF, must be provided with a permanently installed platform.  Installations must meet Occupational Safety and Health Administration and State of Oregon Occupational Safety and Health codes.  All horizontal and vertical runs of pipe prior to an assembly may be required to be sleeved with schedule-40 PVC pipe.  Fire sprinkler system piping will be reviewed on a case-by-case basis regarding sleeving.  
  1. Title 21.24.040 requires access be granted to all premises for inspection of water piping, as described therein. 
  1. Upon completion of a premises-isolation backflow assembly installation, Portland Water Bureau Water Quality Inspection must be notified. Installations must be inspected by a Water Bureau Water Quality Inspector and will require that a Backflow Inspection Fee be paid.
  1. Water service will not officially be activated and is subject to termination without notice until all backflow assembly installation related work has been completed.  Work must be completed prior to temporary or final occupancy being granted by a City of Portland Bureau of Development Services (BDS) Building Inspector.
  1. Assemblies over 2 inches in size (includes 2 inch DCDA/RPDA) must be supported by rigidly mounted metal supports (Standon Pipe Supports or equivalent) underneath the shut-off valves at both ends of the assembly. All above-ground enclosures must be provided with concrete floors/pads, which may not be less than 4 inches in thickness.  If suspended from ceilings, pipe hangers designed to carry the full load of the assembly must be installed.
  1. No pressure testing is to be performed between a premises-isolation assembly and a Water Bureau valve  in the right-of-way.
  1. Assembly installations that incorporate the use of a wye-strainer, the strainer drain valve must not be threaded or have provision that will allow it to be connected to hoses or other plumbed arrangements. 

Additional installation requirements for vaults and enclosures 

When a Double Check Valve Assembly (DCVA) or a Double Check Detector Assembly (DCDA) is installed in a vault the following must be provided: 

  1. Adequate drainage:  Backflow assemblies must not be installed in locations subject to flooding.  Vault/enclosure installations must be provided with adequate drainage and drains may not be connected to sewers of any kind, catch basins, below the flood rim of swales or riverbanks.  A sump pump will be required if vaults are unable to be kept free of standing water.  Sump pump discharge piping must meet vault drainage requirements as stated herein. 
  1. Vault lids with hinged frame and covers (Oldcastle Infrastructure or equivalent): where applicable use Center-Offset frame and cover lids (Oldcastle Infrastructure or equivalent).  These will allow for necessary clearance for ladders in single assembly installations.  For multiple assemblies in a common vault, (Oldcastle Infrastructure or equivalent) centered frame & cover lids may better accommodate installation criteria.  For parking lot, driveway, loading dock areas and/or heavy commercial traffic applications, a minimum of EJ USA Inc. #8217, 36” X 36” or #8217-Double 36” X 74” frame and covers or equivalent must be used.  As determined by the Water Bureau, part #8197, 36” X 36” or #8197-Double, 36” X 74” frame and covers may be required.  Manhole covers are not permitted. 
  1. An approved rigidly mounted ladder, with an extension which extends 3’ above the vault lid (Oldcastle Infrastructure Pull-Up Extension, Bilco LU-1 or equivalent) is required if the vault or chamber is 4’ or greater in depth.  The ladder must be mounted vertically in the entryway of the vault or chamber and be securely anchored at top and bottom.  Ladder orientation must not impede clear access to the assembly and/or vault floor.  The top and bottom rungs must be within 12” of the opening and floor, respectively.  All rungs must have at least 7” of toe clearance, with the exception; if the top rung is at the same elevation as the opening the clearance may be no less than 2.5”.  The ladder must not encroach on the installation clearances for the type of assembly required.  For single & multiple assembly installations, refer to item #2 above to ensure proper ladder placement. 
  1. A moisture-proof light fixture will be required if adequate lighting is not available. 
  1. At least 6’ of vertical headroom is required for all vault, chamber, enclosure and basement installations.   Full opening double doors (Oldcastle Infrastructure 332P-2 or EJ USA Inc. #8127-Double or equivalent) can be used to obtain the 6’ requirement but must encompass the entire lay-length of the assembly and must not encroach on required ladder clearances.  Refer to item #2 above for proper vault lid and frame & cover applications.   
  1. It is recommended when 2” and 1-1/2” Double Check Valve Assemblies (Excludes fire service assemblies, see information under “fire sprinkler services”) are installed below grade the Carson Industries plastic box #1730-18 be used or equivalent.  For 1” and smaller assemblies, Carson Industries box #1419-18 is recommended or equivalent.  All assemblies 2” and smaller (Excludes fire service assemblies, see information under “fire sprinkler services”) must be installed no more than 24” below finished grade.  If installed greater than 24", clearances must meet those specified on page 2 item 9 (second bullet) and be installed in a precast concreate vault that meets vault standards as stated herein. 
  1. In addition to Portland Water Bureau requirements, all vault installations must meet City of Portland Bureau of Development Services standards and will be subject to all applicable permit requirements. 
  1. All backflow assemblies installed below grade must be provided with test cock plugs. 
  1. For assemblies larger than 2” (Includes 2” fire service DCDAs (see fire sprinkler information), only pre-cast vaults (Oldcastle Infrastructure or equivalent) that accommodate the installation criteria will be accepted.  This applies to all below grade new service and retrofit of existing service installations.  See item #2 above for more detailed information regarding vault lids and associated application criteria.  
  1. Above ground enclosure installations may have clearances less than those mentioned previously, provided they are equipped with removable panels, doors and tops that create clearances equal to or greater than those described herein.  Only commercially manufactured prefabricated insulated outdoor enclosures will be approved.  Drawings must be submitted and approved by Water Quality Inspection prior to construction of an alternate type of enclosure.  All exposed piping inside enclosures must be insulated with commercially manufactured pipe insulation or a heat source must be provided. 
  1. All vaults and enclosures for backflow assemblies must be kept free of any debris and/or objects that interfere with these installation requirements and those applicable to OAR 333-061-0071.  Vaults and enclosures must not contain loose fill materials of any kind. 

Premises-isolation reduced pressure backflow assembly (RPBA) installations requirements

  1. An approved airgap must be located directly below the relief valve orifice.  The airgap must be at least twice the inside diameter of the supply piping measured vertically above the top of any drain or receiving vessel.  The air-gap must never be less than 1”.  A RPBA must always be installed 12” above finished grade or the 100-year flood-plain, whichever is greater and meet all applicable drainage requirements unless an approved alternate enclosure is able to meet all applicable criteria as stated herein.  See Item #1on the first page backflow assembly installation requirements for more detailed AFF elevation criteria.
  1. When a RPBA is installed in an above ground enclosure, the enclosure drain must drain to finished grade and be able to discharge the full rated flow of the relief-valve.  The relief-valve must be located 12” above finished slab elevation. 
  1. When a RPBA is installed in a vault or enclosure in a berm or hillside, a horizontal boresight drain to daylight must be provided. The drain must discharge to finished grade and/or be above the 100-year flood plain, whichever is greater.  The relief-valve must be located 12” above the top of the drain opening.  The bottom of the discharge end of the bore-sight drain must be at least 12” above the flood rim of any physical feature such as but not limited to; ponds, fountains, lakes, rivers, swales and/or any other type of receiving vessel.  The bore-sight drain must be in a level horizontal orientation and must be screened off at both ends and not have a lay length of greater than 20-feet.  The bore-sight drain must never be connected to a sewer of any kind, catch basins, sumps or dry wells.  The drain must never be less than 12” above the flood elevation of a water source, swale or any other catchment subject to overflow/flooding.
  1. The proposed installation of a RPBA in an area that may be subject to flooding must be reviewed and approved by Portland Water Bureau Water Quality Inspection prior to installation.  Interior and basement installations must provide drainage for the full rated flow of the relief valve and/or the RPBA supply piping must be equipped with an approved Flood Protection Shut Down Valve. 
  1. A RPBA must be installed on all water service connections that pose a risk to health.  The Portland Water Bureau will determine the degree of risk.  RPBA installations must meet applicable Plumbing Code requirements, be compliant with all applicable rules as outlined in Oregon Administrative Rule 333-061-0070 and Title 21 of the City of Portland Water Code. 
  1. A reduced pressure type backflow assembly is required to be installed on all water service connections to premises having private wells, water features, geothermal heating & cooling systems, hydronic heating systems, cooling towers, that have access to rivers, lakes, ponds and/or other water sources that can be connected to; are equipped with storage tanks, rainwater-harvesting (excluding those that simply capture rainwater in containers of less than 50 gallons and gravity-feed to landscape), storm-water or groundwater recovery and reuse systems and/or that use or reuse treated wastewater (grey and/or black-water) on site.  A RPBA will be required to be installed on any water service that provides for the use of water as a medium for purposes other than potable drinking water and/or where the water is treated in any way.  Assemblies must be installed on private property at the property line (service connection/point-of-delivery as defined in OAR), on the centerline of the city water service as it runs perpendicular from the R.O.W. 
  1. A RPBA must be installed on all service connections to industrial premises where complex (degree of complexity to be determined by the Water Bureau) intricate plumbing systems exist. 
  1. Services supplying premises that are equipped with frost-free drain-back yard hydrants and/or Sanitary Yard Hydrants must be equipped with a RPBA.  
  1. A reduced pressure type assembly must be installed on all water service connections to premises with high-rise buildings (high-rise building: where a building is 75-feet or greater above its lowest finished-floor (slab) elevation to top of structure). 
  1. A reduced pressure type backflow assembly will be required on services to premises with piping systems adjacent to waterways that may be subject to immersion due to periods of highwater incidents.  If available, current GIS data will be used to make this determination. 
  1. A RPBA must be installed on domestic water services to mixed-use and multi-tenant premises. 
  1. A RPBA must be installed on domestic water services to premises where shell buildings are constructed or renovated when occupancy is undetermined at the time of construction and/or renovation. 

Requirements for backflow assemblies installed on fire sprinkler water services

  1. A Double Check Detector Assembly (DCDA) is typically the type of backflow assembly installed on fire sprinkler water services.  See note below.  If the fire sprinkler service is fully metered (a meter approved by the Water Bureau for fire flow application and billing purposes) a Double Check Valve Assembly (DCVA) or Reduced Pressure Backflow Assembly (RPBA) may be installed depending on sprinkler system type.  Note: A Reduced Pressure Detector Assembly (RPDA) is required to be installed where; storage tanks are provided, if the structure is considered a “high-rise” (requirement stated herein), if supplying marinas, moorages, premises having docks and piers, when rainwater-harvesting, storm-water and/or groundwater recovery and reuse systems are installed and/or that use or reuse treated wastewater (grey and/or black-water) for the purpose of augmenting the fire sprinkler system in any capacity. 
  1. Backflow assemblies installed on water services for fire use only; must be installed on private property at the property line (service connection/point-of-delivery as defined in the OAR) on the centerline of the city water service as it runs perpendicular from the R.O.W.  Assemblies approved to be installed inside buildings or structures at the water riser/supply pipe, the riser/supply pipe location must meet location criteria as stated herein.  If the available area between a building and the property line is adequate (determined by the Bureau), the vault, chamber or housing for the type of backflow assembly required must be installed outside the confines of the building or structure.  If the available area is not able to accommodate the enclosure required (determined by the Bureau), the assembly must be installed on the water supply riser/supply pipe and conform to the AFF criteria on page 1, item 1of this document.  The water riser/supply pipe must be installed 12” from the foundation frontage wall to centerline of pipe on the centerline of the city water service as it runs perpendicular from the R.O.W.  Prior to installing a backflow assembly within a building or structure, accurate drawings must be submitted to Portland Water Bureau Water Quality Inspection group for approval.  Drawings must show property lines, building setbacks, identify street frontage, water main, service location and proposed backflow assembly type and location.  An inspection fee must be paid to the Water Bureau prior to replacement of an existing assembly or newly installed assembly on a dedicated fire service.  Where existing fire sprinkler system water piping is significantly remodeled (significance determined by the Bureau) or modified, unapproved assemblies and or devices are to be replaced with those currently approved.  The installation must be compliant with this code and/or any applicable OAR Chapter 333 Rules.  See OAR 333-061-0070, Section 14, which specifically addresses existing installations.  Additionally, all piping for fire sprinkler system backflow assembly installations must be compliant with the local Fire code.  Underground piping requires a minimum 3 feet of cover and may also require a permit be taken out from the Fire Marshal’s office. 
  1. Where anti-freeze compounds, chemicals, gases or any other additives are added to a fire sprinkler system, a Reduced Pressure Detector Assembly (RPDA) will be required.  Where it is possible for a fire sprinkler system to be connected to or be augmented by any auxiliary water source a RPDA will be required.  The RPDA must be installed at the service connection/point-of-delivery to the premises as outlined herein and as defined by OAR Chapter 333-061-0020.  All applicable RPBA installation criteria will apply.  Fire systems that incorporate the use of storage tanks must be equipped with a RPDA and are required to be installed at the service connection/point-of-delivery to the premises as outlined herein. 
  1. When a DCDA is installed in a vault the metered by-pass must be plumbed on the side of the assembly opposite of the ladder.  4” clearance is required between the wall and the bypass, 24” clearance in front, 12” underneath, 3” at both ends and 36” vertically above the assembly body.  Vaults must accommodate 6-feet of vertical headroom or have hinged double door opening frame and covers that accommodate the entire lay length of the assembly.  Find more information related to vault lid and door applications

Bypass meters equipped with touchread register and touch pad or radio signal transmitters

  1. All Double Check Detector Assemblies (DCDA’s) and Reduced Pressure Detector Assemblies (RPDA’s) installed on fire services must be equipped with a Water Bureau approved bypass meter and compatible touchpad.  The touchpad must be accessible from the right-of-way. 
  1. Only 5/8”x 3/4” Neptune T-10 meters with PROREAD or AUTOREAD registers are to be used.  Registers must read in cubic feet.  Touchpads must be compatible with these meters.  Compatible touch-pads for the above meter are Neptune model #12081-000 (wall mount application), Neptune model 12223-150 (vault door application, requires 1 ¾” hole). 
  1. All wiring from the touch-pad to the bypass meter must be insulated 1 pair solid 22 AWG copper wires secured so as not to interfere with the operation and maintenance of the backflow assembly. Wires must not encumber the vault opening or ladder.  Where the touch-pad wire follows the path of other electrical wiring, shielded wire as described above must be used. Splices must be made with 3M Scotchlok moisture resistant connectors, part number UR or UY or equivalent. All splices must be accessible.  
  1. Touch-pad mounting options: 
  • On an outside building wall, at a height between 1’ and 5’ above the floor or finished grade and within 50’ of the backflow assembly.  All wires running from the bypass meter to the touch-pad must be in conduit. 
  • May be mounted on the vault door.  This orientation should locate the touch-pad near the hinged portion of the door so as not to stress the wire between the touch-pad and meter when the door is fully opened. 
  • May be installed in the concrete portion of the vault top, the touch pad must be easily accessible for replacement. 
  • If touch-pad wire must be run underground the wire must be routed through PVC conduit from the meter to the touch-pad. 
  • Touch-pads not installed in vault doors or on a building face must be installed using the Brooks #37, 12” X 20” box w/T&R lid.   
  • Touch-pads or transmitters must be rigidly mounted and be serviceable.  Mounting hardware must be of a type whereby removal and reinstallation may be accomplished without damaging the unit.