32A-124 NFPA 13R notesBruce,
I’m in no sense a fire protection engineer, and this type of setup may not be allowed in this situation, but I have seen this type of valve (link) used before to isolate the domestic
water demand.
http://tyco-fire.com/TFP_common/RSV-1flyer.pdf
NFPA 13R (some is not relevant)
6.6 Water Supply.
6.6.1 Every sprinkler system shall have at least one automatic
water supply.
6.6.2 The water supply shall be capable of supplying the system
demand for at least 30 minutes. (See 6.8.1.2.)
6.6.3* The water supply source shall be one of the following:
(1) A connection to a reliable waterworks system with or without
a pump, as required
(2) An elevated tank
(3) A pressure tank installed in accordance with NFPA 13, Standard
for the Installation of Sprinkler Systems, and NFPA 22, Standard
forWater Tanks for Private Fire Protection
(4) A stored water source with an automatically operated
pump
6.6.4 Where a fire pump is installed, the fire pump shall be
installed in accordance with NFPA 20, Standard for the Installation
of Stationary Pumps for Fire Protection.
6.6.5* Domestic demand shall be included as part of the overall
system demand for systems with common domestic/fire
mains where no provisions are made to prevent the domestic
waterflow upon sprinkler system activation.
6.6.6 Sprinkler systems with non-fire protection connections
shall comply with Section 7.6 of NFPA13, Standard for the Installation
of Sprinkler Systems.
6.7 Installation of System Components.
6.7.1 Valves.
6.7.1.1 A single control valve arranged to shut off both the
domestic system and the sprinkler system shall be installed for
systems with common sprinkler/domestic mains unless a separate
shutoff valve for the sprinkler system is installed in accordance
with 6.7.1.2.
6.7.1.2 The sprinkler system piping shall not have a separate
control valve installed unless supervised by one of the following
methods:
(1) Central station, proprietary, or remote station alarm service
(2) Local alarm service that causes the sounding of an audible
signal at a constantly attended location
(3) Valves that are locked open
6.7.1.3 Aseparate shutoff valve shall be installed for the domestic
water supply in installations having a common sprinkler/
domestic main.
6.7.1.4 System control or shutoff valves shall be of the slowclosing
type unless they meet the requirements of 6.7.1.5.
6.7.1.5 System control or shutoff valves on backflow prevention
devices that are 2 in. (50 mm) or less in nominal size shall
not be required to comply with 6.7.1.4.
6.7.1.6 A listed backflow prevention assembly shall be considered
a check valve, and an additional check valve shall not be
required.
A.6.8.1.2 It is intended that the design area is to include up to
four adjacent sprinklers that produce the greatest water demand
within the compartment. [See Figure A.6.8.1.2(a) and Figure
A.6.8.1.2(b).]
Residential sprinklers are currently listed for use under
flat, smooth, horizontal ceilings only. Sloped, beamed, and
pitched ceilings could require special design features such as
larger flows or a design for five or more sprinklers to operate
in the compartment.