9.2 Cross-Connection Control & Backflow Prevention Assemblies (OAR 333-061-0070)

6.3 Cross-Connection Control & Backflow Prevention Assemblies (OAR 333-061-0070)

Distribution piping networks exist to deliver pure, uncontaminated drinking water. However, every service connection introduces a potential entry pathway for dangerous pollutants or lethal biological and chemical contaminants to enter the public main through cross-connections.

In Oregon, cross-connection control is governed by OAR Chapter 333, Division 061-0070, which places direct legal responsibility on public water purveyors to implement, monitor, and enforce cross-connection control programs throughout their service territories.

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Fundamental Terminology & Physics of Backflow

• Cross-Connection: Any actual or potential physical connection or structural arrangement between a public or private potable water supply system and any plumbing fixture, tank, industrial equipment, or conduit containing liquids, gases, chemicals, or non-potable mixtures.
• Backflow: The unwanted reversal of the normal flow of water or mixtures of water and other liquids, gases, or other substances into the distribution pipes of a potable water supply.
• Backpressure: A condition where the hydrostatic pressure in a customer's non-potable internal plumbing system exceeds the incoming supply pressure of the public water distribution main. Backpressure is generated by:
  • Downstream booster pumps (e.g., tall building booster systems, car wash pumps).
  • Thermal expansion in closed hot water boiler loops or heating systems.
  • Interconnections with private auxiliary water supplies (e.g., irrigation wells, recycled water storage).
  • Elevated storage tanks or tall industrial piping risers ($1\text{ ft elevation} = 0.433\text{ psi}$). If an industrial tank sits $100\text{ feet}$ above the street main, it exerts $43.3\text{ psi}$ of backpressure.
• Backsiphonage: A condition where sub-atmospheric (negative) pressure develops within the public water supply line, creating a vacuum that siphons non-potable liquids back into the drinking water system. Backsiphonage is triggered by:
  • Catastrophic distribution main breaks draining downstream pipes by gravity.
  • High-velocity fire pumping demands drawing dynamic pressure below zero.
  • Dewatering mains for maintenance repairs.
  • Undersized distribution piping during peak concurrent user demands.

   BACKPRESSURE DYNAMICS                          BACKSIPHONAGE DYNAMICS
   
   High Downstream Pressure                       Negative Supply Pressure (Vacuum)
   [Booster Pump / Boiler]                        [Main Break / Fire Pumping]
           │                                              │
           ▼ ($P_{\text{customer}} > P_{\text{main}}$)                 ▼ ($P_{\text{main}} < 0\text{ psi}$)
   ────────────────────────                       ────────────────────────
   Contaminants forced back into main!            Contaminants siphoned back into main!

Contamination vs. Pollution

Oregon administrative rules divide cross-connection hazards into two distinct regulatory risk categories:

1. Contamination (High Health Hazard): Any impairment of potable water quality by sewage, industrial chemicals, toxic heavy metals, bacteriological pathogens, or radioactive substances that creates an actual danger to public health through acute poisoning, chronic chemical toxicity, or waterborne disease transmission. Examples: chemical plating baths, hospital mortuaries, landscape irrigation lines injected with fertilizers/pesticides, radiator cooling systems, commercial car washes.
2. Pollution (Low Non-Health Hazard / Aesthetic Hazard): Any impairment of potable water quality that adversely alters aesthetic properties (taste, odor, color, or turbidity) but does not endanger human health. Examples: commercial food processing lines (beverage syrups, non-toxic food dyes, vegetable oils), steam table loops without toxic chemical additives, residential fire sprinkler systems without chemical additives.

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Oregon Administrative Framework: OAR 333-061-0070 to 0074

Every water supplier must run a cross connection control program. The supplier's responsibility runs from the source to the point of delivery (POD) to the customer's premises. Key requirements:

• Local authority (community systems): an ordinance or other enabling authority that lets the supplier discontinue service for failure to remove or protect a cross connection, or to install, maintain or test a required assembly.
• Written program plan (community systems with 300 or more connections): a list of health-hazard premises (including those on Table 46, Premises Requiring Isolation), assembly and test records, public education, a list of certified staff, and written procedures for hazard evaluation, notification, enforcement and the protection required by Table 47, Backflow Prevention Methods.
• Certified Cross Connection Specialist: community systems with 300 or more service connections must have at least one, unless OHA exempts them (OAR 333-061-0073). Specialists renew every two years with 0.6 CEU of cross-connection training.
• Testing (OAR 333-061-0070(6)): approved air gaps, devices and assemblies are inspected or tested by an OHA-certified backflow assembly tester with a calibrated gauge:
  1. at installation, repair or relocation;
  2. at least once every 12 months;
  3. more often for assemblies that repeatedly fail or protect health hazards;
  4. after a backflow incident; and
  5. after an air gap is re-plumbed. Journeyman and apprentice plumbers who complete an OHA-approved tester course may also test (OAR 333-061-0072).
• Test reports: the tester produces three copies (tester, customer and supplier) within 10 working days.
• Annual Summary Report: community systems submit it to OHA before the last working day of March, and pay an annual program fee based on service connections.
• Non-community systems: owners must keep cross connections eliminated or isolated, survey annually, and test assemblies annually.
• Approved assemblies: listed by the USC Foundation for Cross-Connection Control and Hydraulic Research (or an equivalent OHA-approved laboratory), installed under OAR 333-061-0071 and the Oregon Plumbing Specialty Code, and tested by USC Manual (10th edition) procedures.

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Approved Backflow Prevention Assemblies & Devices

To be legal in Oregon, all assemblies must be approved by the University of Southern California Foundation for Cross-Connection Control and Hydraulic Research (USC-FCCCHR) and listed on the OHA Approved Backflow Assemblies List.

1. Air Gap (AG)

An Air Gap is an unobstructed vertical physical separation through ambient atmosphere between the lowest opening of any pipe supplying potable water to a tank, plumbing fixture, or device and the flood-level rim of the receiving vessel.

• Dimensional Rules: The vertical air gap distance must be at least twice the inside diameter of the supply pipe ($2 \times D$), and under no circumstances less than $1.0\text{ inch}$ ($25\text{ mm}$).
• If a vertical wall sits closer than $3$ pipe diameters to the opening, or if two intersecting walls are nearby, the air gap dimension must increase to three times the pipe diameter ($3 \times D$).
• Degree of Hazard & Capability: Approved for High Health Hazards and Low Hazards; protects against both Backpressure and Backsiphonage. It represents the ultimate, foolproof backflow barrier provided it is not bypassed with a hose.

2. Reduced Pressure Backflow Assembly (RPBA / RP)

The RPBA is the highest-level mechanical backflow prevention assembly manufactured.

   REDUCED PRESSURE BACKFLOW ASSEMBLY (RPBA)
   
   Shutoff #1       Check Valve #1         Check Valve #2       Shutoff #2
      [ | ] ───────►   [ / ]   ──┬───►        [ / ]    ───────►   [ | ]
        │                │       │              │                   │
      Cock 1           Cock 2    │            Cock 3              Cock 4
                                 ▼
                    [Differential Relief Valve] ──► Dumps to Atmosphere!
                     (Opens when ΔP < 2.0 psi)

• Internal Components: Two independently acting, internally spring-loaded check valves separated by a hydraulically operating intermediate chamber with a differential pressure relief valve. Equipped with two full-port resilient-seated shutoff valves and four field test cocks.
• Operating Mechanics: The intermediate relief valve diaphragm monitors the pressure difference between the supply side of Check #1 and the intermediate chamber. The internal relief valve spring is calibrated to pop open to atmosphere whenever the differential pressure drops below $2.0\text{ psi}$ ($14\text{ kPa}$).
• Fail-Safe Protection: If Check #2 leaks under backpressure and Check #1 fouls on grit, or if severe backsiphonage occurs, the relief valve instantly vents all intermediate liquid out the bottom discharge port into the atmosphere. The pressure in the intermediate chamber is mechanically maintained at least $2.0\text{ psi}$ lower than the supply pressure, making reverse flow hydraulically impossible.
• Degree of Hazard & Capability: Approved for High Health Hazards (Contamination) and Low Hazards; protects against both Backpressure and Backsiphonage.
• Installation Rules (OAR 333-061-0071(7)): Install horizontally unless approved for vertical use, above the 100-year flood level, with an approved air gap drain, and never with an extended or plugged relief valve. It may not go in an enclosed vault or box unless a bore-sighted drain to daylight can carry the full relief discharge, because a submerged relief port defeats the assembly. Above five feet a permanent OR-OSHA-compliant platform is needed, and common practice keeps the assembly at least 12 inches above grade.

3. Double Check Valve Assembly (DCVA)

• Internal Components: Two independently acting, internally spring-loaded check valves, two resilient-seated shutoff isolation valves, and four field test cocks. Does not contain a relief valve.
• Operating Mechanics: Check Valve #1 must hold at least $1.0\text{ psi}$ in the direction of flow; Check Valve #2 must hold at least $1.0\text{ psi}$.
• Degree of Hazard & Capability: Approved strictly for Low Non-Health Hazards (Pollution / Aesthetic Hazards); protects against both Backpressure and Backsiphonage.
• Crucial Limitation: NEVER permitted for high health hazards. If an industrial chemical or poison is present downstream and both check valves foul on sediment, the assembly has no relief valve to vent the contaminant, allowing it to enter the potable water main unnoticed.
• Installation Rules: May be installed in sub-grade vaults or pits provided the vault has adequate drainage, test cocks are plugged, and minimum clearances are maintained for testing.

4. Pressure Vacuum Breaker (PVB) & Spill-Resistant Vacuum Breaker (SVB)

• Internal Components: An independently operating spring-loaded check valve and an independently operating spring-loaded air inlet valve opened by spring force when pressure drops. Includes two shutoff valves and two test cocks.
• Operating Mechanics: Under normal pressure, the check valve opens and line pressure seals the air inlet shut. If supply pressure drops to $1.0\text{ psi}$, the spring drives the air inlet valve wide open, breaking the vacuum.
• Degree of Hazard & Capability: Approved for High Health Hazards and Low Hazards, but for BACKSIPHONAGE ONLY. CANNOT withstand backpressure (backpressure forces the air inlet shut and pushes non-potable water through the check valve).
• Continuous Pressure Rating: PVBs are rated for continuous operating pressure (can remain under pressure for $>12\text{ hours}$ continuously).
• Installation Rules: Must be installed at least $12\text{ inches}$ above the highest downstream piping, sprinkler head, or outlet.

5. Atmospheric Vacuum Breaker (AVB)

• Internal Components: A non-testable mechanical device consisting of a moving float/poppet check. Contains no shutoff valves, no springs, and no test cocks.
• Operating Mechanics: Forward water flow lifts the poppet to seal the air inlet. When flow ceases or line pressure drops, the poppet drops by gravity, venting the downstream conduit to atmosphere.
• Operational Restrictions & Hazards:
  1. Backsiphonage ONLY; cannot withstand backpressure.
  2. Non-Continuous Pressure ONLY: Under OAR 333-061-0071(10), an AVB must never be subjected to continuous pressure for more than 12 hours in any 24-hour period. If left under continuous pressure, the rubber poppet adheres to the air inlet seat, freezing it in the closed position and rendering it completely useless during a vacuum event.
  3. No Downstream Shutoff Valves: No valves may be installed downstream of an AVB.
  4. Must be installed at least $6\text{ inches}$ above the highest downstream outlet.

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Master Comparative Matrix: Backflow Prevention Technology