9.3 Testable Assemblies: RP, Double Check, PVB & SVB; Location, Testing & Virginia Certification

Reduced pressure principle assembly (RP) — ASSE 1013 (IPC 608.14.2)

Construction: two independently acting, spring-loaded check valves with a differential pressure relief valve in the zone between them, two resilient-seated shutoff valves, and four test cocks. Test cock 1 is upstream of shutoff 1, test cock 2 is between shutoff 1 and check 1, test cock 3 is in the zone between the checks, and test cock 4 is between check 2 and shutoff 2.

How it works:

• The first check holds the zone at a lower pressure than the supply. In normal service, the relief valve stays closed as long as the supply pressure exceeds the zone pressure by more than its opening point, which is about 2 psi in standard field testing.
• If backsiphonage drops the supply pressure, the relief valve opens and drains the zone to atmosphere.
• If backpressure combines with a leaking second check, zone pressure rises, the differential drops, and the relief valve opens to discharge.
• Visible discharge from the relief port tells the owner that something is wrong.

Code rules:

• An RP may be installed where it is under continuous pressure.
• The relief opening shall discharge by air gap and shall be prevented from being submerged. Do not install an RP in a pit or vault that can flood, because flood water could reach the relief port.
• Reduced pressure detector assemblies for fire protection meet ASSE 1047.
• An RP is the assembly required for high-hazard backpressure (608.17.6) and is accepted for any hazard in Table 608.1.

Double check assembly (DC) — ASSE 1015 (IPC 608.14.7)

Two independently acting checks, two shutoff valves and four test cocks, with no relief valve. It works under continuous pressure and protects against backpressure and backsiphonage, but only for low hazard (Table 608.1). If both checks foul, nothing discharges to warn anyone. Double check detector fire protection assemblies meet ASSE 1048.

Pressure vacuum breaker (PVB) — ASSE 1020, and spill-resistant vacuum breaker (SVB) — ASSE 1056 (IPC 608.14.5)

• PVB: a spring-loaded check valve and a spring-loaded air inlet valve, two shutoff valves and two test cocks. It works under continuous pressure, at high or low hazard, against backsiphonage only.
• SVB: designed so the air inlet closes before water can spill when pressure returns. It is used indoors where a PVB's spill would cause damage. It has one test cock and a vent valve.
• Height: both must be installed with the critical level at least 12 inches above all downstream piping and outlets.
• PVBs shall not be installed where spillage could cause damage to the structure.

Where assemblies go (IPC 608.15, as amended by Virginia)

• Virginia 608.15: access must be provided for inspection, testing, service, repair and replacement. Backflow prevention assemblies must be installed between 12 inches and 60 inches from grade, floor level or service platform, and as the manufacturer specifies. Where the manufacturer's listed installation height conflicts, the manufacturer's listed height applies. Access must also be provided to backflow prevention devices.
• 608.15.1: outdoor enclosures meet ASSE 1060.
• 608.15.2: backflow preventers may not be located where they could freeze, unless they can be removed with unions or are protected by heat, insulation or both.
• 608.15.2.1: piping from an RP's relief port, or from an air gap fitting, discharges to an approved indirect waste receptor or to the outdoors where it will not cause damage or a nuisance. The receptor and drain must be sized for the maximum relief port discharge published by the manufacturer, which can be large on bigger assemblies.

Inspection and testing (IPC 312.10)

• 312.10.1: annual inspections of all backflow prevention assemblies and air gaps, to confirm the assemblies work and the air gaps exist.
• 312.10.2: RP, double check, PVB, RP detector, double check detector and SVB assemblies, and hose connection backflow preventers, must be tested at the time of installation, immediately after repairs or relocation, and at least annually. Testing follows ASSE 5013, 5015, 5020, 5047, 5048, 5052 or 5056, or CSA B64.10 or B64.10.1. Test gauges must meet ASSE 1064.

Field test outline (ASSE 5000-series procedures):

Virginia backflow prevention device worker certification

• § 54.1-1128 defines a backflow prevention device worker as an individual who maintains, repairs, tests or periodically inspects cross-connection control devices such as RP assemblies, double check assemblies, double check detector assemblies and pressure vacuum breakers.
• § 54.1-1129 B: state certification is voluntary. Uncertified workers may practice where the locality's program allows it, but no one may present themselves as certified without Board certification. Localities must accept Board certification as proof of experience and training without another exam.
• 18VAC50-30-42 qualifications: 4 years of practical experience in water distribution systems and at least 32 hours of formal vocational training at a Board-approved school, or 7 or more years of experience and 16 hours of training. The Board accepts ASSE standards for testing procedures and requires backflow training to include a wet lab.
• The PSI backflow prevention device worker exam has 40 items with a passing score of 30, in 150 minutes.
• The certification runs on a 2-year cycle (18VAC50-30-120 B), and the renewal fee is $110 (18VAC50-30-120 G).
• § 54.1-1134: a water purveyor or building official who believes a certified worker is incompetent, shown by egregious or repeated violations of the ASSE standards in the plumbing code, must report it to the Board.