6.3 Installation, Testing & Certification of Backflow Preventers

6.3 Installation, Testing & Certification of Backflow Preventers

Exam Focus: Installing a backflow prevention assembly incorrectly is just as dangerous as failing to install one at all. Licensing exam candidates must master the location and access rules under MPC Section 608.15, the strict statutory ban on subterranean RPZ pit installations, indirect relief valve drainage requirements, the ASSE 5110 tester certification standards, and the step-by-step differential pressure test procedures (including the critical 2.0 psid relief opening threshold).

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1. Physical Location, Clearances & Elevation Rules (MPC 608.15)

Under MPC Section 608.15 (Location of backflow preventers), backflow prevention assemblies and devices must be installed in a location that provides access for routine inspection, testing, maintenance, and overhaul, in accordance with the approved manufacturer's installation instructions. Enclosing testable assemblies inside finished drywall cavities, positioning them above inaccessible drop ceilings, or placing them in crawlspaces lacking adequate headroom constitutes a code violation.

Vertical Elevation Standards for RPZ Assemblies (assembly listings and utility standards)

To ensure proper drainage from the differential relief port, protect the assembly from standing water, and permit an inspector to attach test hoses:

  ELEVATION CLEARANCES FOR REDUCED PRESSURE PRINCIPLE (RPZ) ASSEMBLIES
  +-------------------------------------------------------------------------+
  |                                                                         |
  |   MAXIMUM HEIGHT: 60 INCHES (5 FEET) ABOVE FINISHED FLOOR OR GRADE       |
  |   (If > 60", a permanent OSHA-compliant working platform is mandatory) |
  |                                                                         |
  |                             [ RPZ ASSEMBLY ]                            |
  |                              |    (O) (O)    |                          |
  |                              +-------v-------+                          |
  |                                      | Relief Port                      |
  |                                      v                                  |
  |   MINIMUM HEIGHT: 12 INCHES (1 FOOT) ABOVE FINISHED FLOOR OR GRADE      |
  |                                                                         |
  |   ===================================================================   |
  |   FINISHED CONCRETE FLOOR / GRADE                                       |
  +-------------------------------------------------------------------------+

1. Minimum Elevation: The lowest point of the assembly (the bottom of the differential relief valve discharge port) must be installed not less than 12 inches (305 mm) above the finished floor or finished grade.
2. Maximum Elevation: The centerline of the assembly must be installed not more than 60 inches (1,524 mm / 5.0 feet) above the finished floor or permanent work platform. If an assembly is installed higher than 5 feet above the floor, a permanent, structurally approved work platform, catwalk, or fixed stairway conforming to MIOSHA standards must be provided.
3. Lateral Clearances: A minimum unobstructed working clearance of not less than 24 to 36 inches must be maintained in front of all test cocks to accommodate the differential pressure test gauge and allow technicians to remove the check valve access covers without obstruction.
4. Orientation: Assemblies must be installed strictly in the orientation for which they are certified by ASSE (typically horizontal flow). Certain specialized assemblies are listed and marked for vertical-up flow; however, an assembly listed only for horizontal installation can never be installed vertically.

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2. Prohibited Installations: The Submerged Pit Hazard (MPC 608.15.2)

One of the most dangerous cross-connections in the plumbing industry occurs when an RPZ backflow preventer is installed below grade in a pit or utility vault.

+-------------------------------------------------------------------------+
|                 ABSOLUTE CODE PROHIBITION: MPC 608.15.2                 |
|                                                                         |
|    REDUCED PRESSURE PRINCIPLE (RPZ) BACKFLOW PREVENTERS SHALL NEVER     |
|       BE INSTALLED IN PITS, VAULTS, OR SUBTERRANEAN ENCLOSURES!         |
+-------------------------------------------------------------------------+

The Deadly Physics of Pit Submersion

1. Pit Flooding: Underground vaults, meter pits, and manholes are subject to environmental flooding from high water tables, surface stormwater runoff, and catastrophic pipe leakage. In addition, outdoor pits frequently collect yard runoff containing animal feces, fertilizers, and street silt.
2. Atmospheric Vent Opening: During a backsiphonage event (such as a city water main break), the internal differential pressure of the RPZ drops to zero. As designed, the internal spring forces the intermediate relief valve wide open to vent to atmosphere.
3. Contaminant Ingestion: If the pit is flooded and the relief valve port is submerged, the negative pressure in the water supply does not suck air—it siphons the toxic, pathogen-laden floodwater directly through the open relief port and straight into the potable drinking water supply!
4. Code Mandate (MPC 608.15.2): The relief opening of a reduced pressure principle assembly must not be submerged, so RPZ assemblies must be installed in above-ground mechanical rooms or approved above-ground heated fiberglass/aluminum outdoor enclosures (e.g., ASSE 1060 insulated enclosures) equipped with gravity daylight drain ports.

Contrast with Double Check Valves: Unlike RPZs, Double Check Valve Assemblies (DCVAs / ASSE 1015) have no atmospheric vents and may be installed in subterranean utility vaults, provided the vault is clean, dry, protected against freezing, and equipped with a gravity drain or sump to prevent water accumulation during testing.

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3. Relief Valve Drainage & Air Gap Funnels (MPC 608.15.2.1)

An RPZ differential relief valve is engineered to spit water during minor pressure surges and dump massive volumes of water (from 20 to over 200 GPM depending on pipe diameter) in the event of a fouled check valve or backsiphonage event.

Drainage Installation Rules

1. Prohibition of Direct Plumbing (No Hard Connections): The relief valve discharge opening SHALL NEVER BE DIRECTLY CONNECTED (HARD-PIPED) to any drainage pipe, sewer lateral, waste line, or soil stack. Hard-piping a relief valve to a sanitary drain creates a direct cross-connection between the sewer and the backflow preventer.
2. Manufacturer Air Gap Funnel Fitting: Drainage piping connected to an RPZ relief port must terminate through an approved, factory-manufactured air gap funnel fitting specifically listed for that assembly.
3. Air Gap Dimension: The air gap between the relief valve discharge outlet and the receiving funnel must be not less than twice the internal diameter ($2 \times D$) of the relief valve discharge bore, and never less than 1.0 inch (25.4 mm).
4. Drain Sizing and Receptor Capacity: The waste receptor (floor sink, hub drain, or trench drain) receiving the indirect discharge must be sized with an outlet capacity capable of handling the maximum rated hydraulic discharge flow of the RPZ without overflowing into finished floor areas.
5. Discharge Termination: Where relief drainage piping terminates outdoors, it must discharge through a downward-facing elbow located between 2 inches and 6 inches above finished grade, equipped with a stainless steel insect screen, in a location that will not discharge onto pedestrian walkways (preventing winter slip hazards from ice formation).

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4. Michigan Annual Testing & Certification Mandates

Under EGLE Part 14 Rules (R 325.11404) and Michigan's added MPC 312.10, 312.10.1 and 312.10.2 (R 408.30725f, R 408.30725g, R 408.30725h), backflow prevention assemblies are not "install-and-forget" items. Michigan's 312.10.1 requires inspections of all backflow prevention assemblies and air gaps after installation or relocation to determine whether the assemblies are operable and the air gaps exist, and 312.10.2 requires RPZ, double check, pressure vacuum breaker, RP detector fire protection, double check detector fire protection, spill-resistant vacuum breaker, and hose connection backflow preventers to be tested at the time of installation, immediately after repairs, or at the time of relocation, with gauges complying with ASSE 1064 and test procedures following ASSE 5013, 5015, 5020, 5047, 5048, 5052, 5056, CSA B64.10, or CSA B64.10.1. Because check valve springs fatigue, rubber discs deteriorate, and grit scores valve seats, assemblies must be certified through mandatory field testing.

The Four Mandatory Testing Milestones

All testable backflow prevention assemblies (RPZ, DCVA, PVB, SVB) must undergo certified diagnostic field testing:

1. Upon initial installation prior to the plumbing system being commissioned or placed into service.
2. Immediately following any repair, rebuilding, or replacement of internal components (such as new springs, check modules, or diaphragms).
3. Immediately after any physical relocation of the assembly from one piping run to another.
4. At least once annually (every 12 months) thereafter as part of the facility's ongoing cross-connection compliance program.

Tester Qualifications & Documentation

• Certified Tester Requirement: In Michigan, field testing must be conducted by an individual who holds an active ASSE 5110 Backflow Prevention Assembly Tester Certification and is registered with the local water utility.
• Inspection Tag: Upon passing the diagnostic test, the certified tester must complete and secure an approved, durable, weather-resistant inspection tag directly to the assembly. The tag must record:
  • Tester's full name and ASSE 5110 certification number.
  • Name of the certified testing agency or licensed plumbing contractor.
  • Date of the test.
  • Differential pressure test kit serial number and annual calibration date.
  • Recorded test data (Check 1 differential psid, Check 2 hold, Relief valve opening point psid, Shutoff valve hold).
• Reporting Window: A formal written test report must be filed with the local water purveyor (municipal water department) within 30 calendar days of test completion.

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5. Diagnostic Field Testing Procedures: The Differential Pressure Kit

Field testing of testable assemblies is executed using a specialized differential pressure test kit (certified under ASSE 1064) consisting of three flexible hoses (High Pressure [Red], Low Pressure [Green], Bypass [Blue]), a precision differential pressure gauge reading from 0 to 15 psid, and needle control valves.

                     DIFFERENTIAL TEST GAUGE HOOKUP (RPZ) 

                        [ GAUGE: 0 - 15 PSID ]
                            /     |     \
                     High  /     Low     \  Bypass
                    Valve /     Valve     \ Valve
                         /        |        \
             (Red Hose) /   (Green Hose)   \ (Blue Hose)
                       /          |          \
                      v           v           v
       Inlet       TC #1       TC #2       TC #3       TC #4       Outlet
       ----[SHUTOFF 1]--(O)-----( \ )---(O)-----( \ )---(O)---[SHUTOFF 2]---->
                               Check 1   ^     Check 2
                                         | Intermediate Zone
                                         v
                                   [RELIEF VALVE]

Test Cocks Layout on an RPZ (Numbered 1 to 4 with flow direction)

• Test Cock 1: Located on the inlet side of Shutoff Valve 1 (upstream supply pressure).
• Test Cock 2: Located on the inlet side of Check Valve 1 (upstream pressure within assembly).
• Test Cock 3: Located in the intermediate differential pressure zone (between Check 1 and Check 2).
• Test Cock 4: Located on the downstream side of Check Valve 2 (inlet to Shutoff Valve 2).

Step-by-Step RPZ Field Test Protocol (ASSE 5110 / AWWA Method)

Step 1: Pre-Test Inspection & Bleed

1. Notify facility occupants of brief water interruption.
2. Inspect assembly for physical damage, illegal bypasses, or relief leaks.
3. Open and flush test cocks 1, 2, 3, and 4 to blow out sand, scale, and foreign debris, then close all test cocks.

Step 2: Testing the Differential Relief Valve Opening Point

1. Connect the High-Pressure Hose to Test Cock 2.
2. Connect the Low-Pressure Hose to Test Cock 3.
3. Open Test Cocks 2 and 3, and bleed all air from the test kit gauge using the high and low bleed needle valves.
4. Close Shutoff Valve 2 (downstream isolation valve).
5. Slowly open the High Control needle valve on the test kit, bleeding high-pressure water from Test Cock 2 across into Test Cock 3. This slowly increases the pressure in the intermediate zone, simulating a fouled check valve.
6. Observe the differential needle on the gauge as it drops toward zero.
7. Note the exact gauge reading the moment water begins to drip and discharge from the relief valve port.
8. Passing Criterion: The relief valve MUST OPEN AT NOT LESS THAN 2.0 PSID (pounds per square inch differential). If the relief valve fails to discharge before the gauge drops below 2.0 psid, or fails to open completely, the assembly FAILS the test and must be rebuilt.

Step 3: Testing Check Valve 2 for Tightness Against Backpressure

1. Maintain hoses connected to TC 2 and TC 3.
2. Connect the Bypass Hose to Test Cock 4.
3. Open Test Cock 4 and bleed air through the bypass valve.
4. Open the bypass needle valve, introducing high pressure downstream of Check Valve 2.
5. If the differential pressure on the gauge drops toward 2.0 psid and water begins discharging from the relief valve, Check Valve 2 is leaking and has failed to hold against backpressure.
6. Passing Criterion: Check Valve 2 must hold tight against backpressure with zero relief valve discharge.

Step 4: Testing Check Valve 1 for Tightness & Minimum Differential

1. Bleed low side and observe the static differential across Check Valve 1.
2. The gauge measures the pressure difference between Test Cock 2 (upstream) and Test Cock 3 (intermediate zone).
3. Passing Criterion: Check Valve 1 must be closed tightly, holding a static differential of at least 5.0 psid (and typically between 6.0 and 10.0 psid).

Step 5: Testing Shutoff Valve 2 for Tightness

1. Close Test Cock 2 and bleed downstream pressure. Check if water continues to leak back from the facility piping through Shutoff Valve 2 into Test Cock 4.
2. Passing Criterion: Shutoff Valve 2 must close bubble-tight to ensure test accuracy.

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6. Diagnostic Troubleshooting Table for Field Testing

When an assembly fails an annual certification test, the certified technician must diagnose the root failure before disassembling internal components:

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7. Realistic Exam Application Scenarios

Scenario A: Mechanical Room Clearance Violation

Exam Scenario: During a rough-in inspection of a new commercial veterinary hospital in Lansing, a plumbing inspector evaluates an ASSE 1013 RPZ installed on a 2-inch cold water branch feeding an animal surgical suite. The installer hung the RPZ directly against the ceiling, 8 feet 6 inches above the floor, directly over an open motor-generator set. The relief valve port has a 3/4-inch PEX pipe clamped directly to the relief bore, terminating into a plastic 5-gallon bucket on the floor.

What specific violations of MPC Section 608.15 exist?

Code Analysis:

1. Access Violation (MPC 608.15): The assembly is mounted at 8'6" (102 inches), far above the 60-inch working height that the assembly listing and MIOSHA access rules contemplate, with no permanent work platform. It cannot be tested, serviced, or rebuilt from the floor, so it fails the access requirement of MPC 608.15.
2. Relief Port Piping Violation (MPC 608.15.2.1): The relief valve discharge cannot be directly clamped or hard-piped to a drainage pipe. It must terminate through an approved manufacturer air gap funnel fitting ($2 \times D$, minimum 1 inch).
3. Discharge Receptor Violation: Discharging into a 5-gallon bucket is illegal. The relief port must discharge indirectly into an approved floor sink or drain receptor capable of accepting full relief valve flow without flooding.
4. Hazardous Location: Installing an RPZ over electrical machinery is prohibited because inevitable relief spitting creates an electrical shock and equipment hazard.

Scenario B: Annual Field Certification Failure

Exam Scenario: An ASSE 5110 certified tester is conducting the annual certification test on a 4-inch RPZ protecting a school heating boiler. When testing the relief valve opening point (Step 2), the tester bleeds the high-control needle valve. The differential gauge needle steadily drops past 2.0 psid down to 0.8 psid before the relief valve finally pops and discharges water.

What is the tester's legal obligation under Michigan EGLE Part 14 and BCC rules?

Code Analysis:

1. Test Failure: The mandatory minimum opening threshold for an RPZ relief valve is 2.0 psid. An opening point of 0.8 psid represents a complete test failure.
2. Safety Danger: Because the relief valve spring is weak, backpressure could force non-potable boiler chemicals into the intermediate chamber without triggering the relief valve to discharge.
3. Tester Action: The tester cannot sign or certify the inspection tag. The assembly must be tagged as FAILED, the facility owner and municipal water purveyor notified, the relief valve dismantled and rebuilt with an approved manufacturer repair kit, and the assembly fully re-tested until it achieves $\ge 2.0\text{ psid}$.