BCAB #1951 - Vacuum-Relief Valve Requirement

January 2, 2025

Re: Vacuum-Relief Valve Requirement

Project Description

The project involves the construction of a new fourplex containing a crawlspace.  Each unit is serviced by a separate municipal water service pipe made of plastic suitable for cold water use only, a shut-off valve, a pressure-reducing valve, a check valve, and an expansion tank.  Each unit has a storage-type service water heater with an integral hot water tank.

Applicable Code requirements (BCBC 2024 Book II (Plumbing Systems))

Sentence 2.6.1.7.(8), Division B, Relief Valves

(8) A vacuum-relief valve shall be installed when any tank may be subject to back-siphonage.

Sentence 2.6.2.2.(1), Division B, Back-Siphonage

(1) Potable water connections to fixtures, tanks, vats or other devices not subject to pressure above atmospheric and containing other than potable water shall be installed so as to prevent back-siphonage in conformance with Sentence (2).

Decision being appealed (Local Authority’s position)

All tanks connected to the municipal water supply require a vacuum-relief valve as protection from back-siphonage.  A check valve does not provide the required protection.

In the Article titled “Back-Siphonage” located in the Subsection titled “Protection from Contamination”, the Code provides a list of devices suitable for preventing back siphonage and a check valve is not included in the list.

Appellant's position

A vacuum-relief valve is not necessary because the check valve protects each tank from back-siphonage into the municipal water supply.

The Code’s requirements regarding protection from contamination are not related to protection from vacuum damage.  Sentence 2.6.2.2.(1), Division B, specifically excludes pressurized water storage tanks.

Appeal Board Decision #1951

The Board varies the decision of the local authority.

It is the determination of the Board that each hot water tank requires a vacuum-relief valve as protection from back siphonage.  However, the Code requirement related to protection from contamination due to back-siphonage is not applicable.

Reason for decision

Each hot water tank may be subject to back-siphonage and a vacuum-relief valve must be installed for that reason.

The check valves installed on the water service pipes protect the water service pipes which are made of plastic that is suitable for cold water use only.  The check valves do not provide the tanks with vacuum-relief to protect them from back-siphonage that may occur in the system or from potential damage when routine maintenance is performed.

The Code requirement related to protection from contamination due to back-siphonage is not applicable because the hot water tanks are subject to pressure above atmospheric and contain only potable water.

Don Pedde
Chair, Building Code Appeal Board