Pressure Relief Valves in Wet Sprinkler Systems

Save Time, Save Water…Save Money

In 2010, NFPA 13, the Standard for the Installation of Automatic Sprinkler Systems, adopted the new standard requiring the installation of pressure relief valves on all wet systems.  Prior to 2010, pressure relief valves were only required downstream of pressure reducing valves and on gridded systems.

The Requirement

AGF’s Model 7000 Pressure Relief Valve

In accordance with NFPA 13 (2010 edition – Sec. 7.1.2), and as maintained in the 2013 and 2016 editions, a wet pipe system shall be provided with a listed relief valve not less than 1/2 in. (12 mm) in size and set to operate at 175 psi (12.1 bar) or 10 psi (0.7 bar) in excess of the maximum system pressure, whichever is greater.  However, where auxiliary air reservoirs are installed to absorb pressure increases, a relief valve shall not be required.*

It should be further noted that Chapter 3 of NFPA 13 (2013 & 2016 editions) has gone to great lengths to define a system.  Section 3.3.22 (2013) and Section 3.3.23 (2016) define a sprinkler system as, “a system that consists of an integrated network of piping designed in accordance with fire protection engineering standards that include a water supply source, a water control valve, a waterflow alarm, and a drain.”

Also, NFPA 13 Section A.3.3.22 (2013) and Section A.3.3.23 (2016) expand on Chapter 3’s definition further, “as applied to the definition of a sprinkler system, each system riser serving a portion of a single floor of a facility or where individual floor control valves are used in a multistory building should be considered a separate sprinkler system.  Multiple sprinkler systems can be supplied by a common supply main.”

The bottom line is that a relief valve must be installed downstream of any control valve – typically, one on every floor of a multistory building being supplied by a single riser (or two where the total square foot area of the floor requires two supply risers).

The current requirement for the installation of pressure relief valves is intended to prevent pressure build-up within the wet pipe system from exceeding the working pressure of the system components, which is traditionally 175 psi (12.1 bar).  It is important to note that the pressure rating of the relief valve indicates an operating range of pressure for both opening and closing of the valve.

Relief Valve Location

The relief valve can be located anywhere on the system.  However, one of the most common and convenient locations is at the floor control assembly.  By installing the relief valve in this location, contractors are typically able to take advantage of the close proximity of a drain riser so that the safe draining of the relief valve can be easily accomplished.

Products like the AGF Models 1011 and 2511 TESTanDRAIN® Valves, 3011 Inspector’sTEST™ Valve and 8011 RiserPACK™ Floor Control Assembly, the Viking EASYPAC Commercial Riser Assembly, the Victaulic® Testmaster™II Style 720 and Series 247 FireLock Zone Control Riser Module, the Tyco Riser Manifold, the Reliable CR Commercial Riser Manifold, and the Guardian 9225 and 9230 Assemblies were developed specifically to provide a convenient location for the installation of a pressure relief valve and the drain line coming from that valve.

Save Water/Save Time

During the installation process, a system needs to be integrity tested by pressurizing the system to typically 200 psi.  However, it is impossible to pressurize a system with a properly working pressure relief valve to a suitable pressure above the intended working pressure.  In order to confirm a leak-free system, it is necessary to first install the system without the relief valves, or remove the relief valves prior to testing.  Unlike other products, the entire AGF TESTanDRAIN® line and the Viking EASYPAC (built with the AGF TESTanDRAIN® M1011A) allow for the installation of pressure relief valves after integrity testing without having to completely drain down the system.  While some water is lost when users open the valve to the drain position in order to isolate the pressure relief valve installation port, the amount is minimal compared to the water lost and the time wasted completely draining a system.

Additionally, changing out an old or damaged pressure relief valve or installing a new pressure relief valve on a TESTanDRAIN® valve is an easy procedure and can be accomplished without removing the TESTanDRAIN® valve from the line or draining down the system – saving water, saving time, and saving money.

Originally printed in the February 2017 edition of Fire Protection Contractor Magazine.