Containment, Isolation, and a Flooded RPZ Vault

The installation fails on four independent points:

• Location: a below-grade vault that fills with groundwater is a flooding location. Reduced-pressure-principle assemblies must be installed where they cannot be submerged, and most model codes and virtually all authorities having jurisdiction require them above grade. Submersion can foul the relief valve and the check valves and defeats the assembly's ability to discharge.
• Relief discharge: the relief port must discharge by gravity through an air gap, with no plug, cap, or reduction. A capped connection is a direct violation and creates a pressurized, unprotectable condition.
• Drainage: the relief discharge must be able to flow at full rate without backing up - an air gap over a properly sized receptor, not a piped connection to a floor drain.
• Access and testing: the assembly must be accessible for testing and repair, installed in the orientation its listing permits, with test cocks usable.

The fix is to relocate the assembly above grade inside the building, with a drain sized for the relief discharge and an air gap, and to revise the plans and obtain approval before the vault is backfilled. This is a change order, not a field correction, and the schedule must absorb it.

The building RPZ provides containment - it protects the public main from anything in the building. It does not protect building occupants from a hazard inside the building. Each hazard needs isolation protection at the point of connection:

• Fertigation: chemical injection is a high hazard. A reduced-pressure-principle assembly is required at the irrigation connection, upstream of the injector, so fertilizer cannot be drawn back into the building's domestic piping. The building RPZ does not satisfy this.
• Dental operatories: each cuspidor water line and each dental unit connection is a cross-connection with a vacuum system on the other side. Protection is required at each unit - typically a vacuum breaker or an air gap at the cuspidor supply - and the shared vacuum system itself must be protected. Three unprotected connections are three violations.
• Antifreeze loop: the glycol loop is a high-hazard connection to the potable supply, and the 1-inch bypass with a gate valve is an uncontrolled, unlisted connection. The bypass must be removed or locked out, and the makeup connection must be through a listed backflow assembly sized for the fill rate. A double-check detector assembly on the fire line does not protect a glycol connection.

Each assembly must be tested and tagged at installation and annually thereafter.

Containment is one assembly at the service entrance protecting the water main and the neighborhood. Isolation is protection at each hazard inside the building protecting the people in it. A medical office with irrigation chemicals, dental vacuum systems, and glycol needs both, and most codes and the facility's insurer will require it.

A realistic path:

1. Immediately submit a revised plan showing the relocated RPZ above grade with an air-gap drain, an RPZ on the irrigation branch upstream of the injector, protection at each dental unit, and a properly protected antifreeze makeup with the bypass removed.
2. Order the assemblies now - lead times, not installation, are usually the schedule driver - and confirm each is listed and sized for the flow.
3. Remove the bypass and cap or lock the connection today; that is a field correction that does not need a new assembly.
4. Schedule installation testing with the fire protection contractor, since the fire line hydrostatic test and the backflow test must be coordinated.
5. Obtain the AHJ's approval of the revised documents before final inspection.

Twenty days is achievable only if the assemblies are ordered immediately and the owner accepts that the vault relocation is a change order. Promising an opening date before the RPZ is above grade and tested is not a schedule, it is a risk.