Check valve at floor control valve

[KLH]

Hello,

What is the purpose of the check valve in Figure A.8.17.5.2.2(b)?

Thanks is advance.

 

[NJ1]

Where is the picture?

 

[pipesnpumps]

Not sure which version you are looking at, but I'm assuming you mean the floor control valve assembly for a combined sprinkler/standpipe system..

I believe that check valve downstream of the floor control valve is to prevent backflow out of the sprinkler system if and when the fire hose connection is used.. (a giant and sudden pressure drop in the standpipe).

 

[cdafd]

because nfpa 13 says so




8.17.5.2.2* The following restrictions shall apply:
(1) Each connection from a standpipe that is part of a combined system to a sprinkler system shall have an individual control valve and check valve of the same size as the connection.
(2) The minimum size of the riser shall be 4 in. (102 mm) unless hydraulic calculations indicate that a smaller size riser will satisfy sprinkler and hose stream allowances.
(3) Each combined sprinkler and standpipe riser shall be equipped with a riser control valve to permit isolating a riser without interrupting the supply to other risers from the same source of supply. (For fire department connections serving standpipe and sprinkler systems, refer to Section 6.8.)

 

[pipesnpumps]

cdafd,

In a hydraulically calculated combined system standpipe, do you agree the minimum size is 4"? The code can be logically read two ways.

It says 6" minimum for combined systems, but then has other verbage that states 4" min. for hydraulically calculated standpipes.. So which do you use?

 

[cdafd]

pipesnpumps'

what nfpa,,, edition,, sections are you referencing??

 

[pipesnpumps]

NFPA 14-2007 for example

7.6.1 Class I and Class III standpipes shall be at least 4 in. (100 mm) in size.

7.6.2 Standpipes that are part of a combined system shall be
at least 6 in. (150 mm) in size.

7.6.3 Where the building is protected throughout by an approved automatic sprinkler system in accordance with NFPA 13, Standard for the Installation of Sprinkler Systems, and NFPA13R, Standard for the Installation of Sprinkler Systems in Residential Occupancies up to and Including Four Stories in Height, the minimum standpipe size shall be 4 in. (100 mm) for hydraulically calculated systems.


I recently had an FPE I trusted tell me that 7.6.3 trumps 7.6.2... I accepted the design because the hydraulic calcs proved it would work, but now I am 2nd guessing myself. 7.6.3 does not seem to apply to combined systems at all..

 

[pipesnpumps]

I should stated, I'm talking about a standpipe in an NFPA 13 compliant building, with Class I hose connections on a combined system..

 

[cdafd]

answer is yes he told you correctly

from nfpa 13:::


8.17.5.2 Hose Connections for Fire Department Use.
8.17.5.2.1 In buildings of light or ordinary hazard occupancy, 2½ in. (64 mm) hose valves for fire department use shall be permitted to be attached to wet pipe sprinkler system risers.
8.17.5.2.2* The following restrictions shall apply:
(1) Each connection from a standpipe that is part of a combined system to a sprinkler system shall have an individual control valve and check valve of the same size as the connection.
(2) The minimum size of the riser shall be 4 in. (102 mm) unless hydraulic calculations indicate that a smaller size riser will satisfy sprinkler and hose stream allowances.
(3) Each combined sprinkler and standpipe riser shall be equipped with a riser control valve to permit isolating a riser without interrupting the supply to other risers from the same source of supply. (For fire department connections serving standpipe and sprinkler systems, refer to Section 6.8.)

 

[pipesnpumps]

Yeah there is obviously some overlap and confusion here..

NFPA 13 8.17.5.2.2(2) says you /can/ go less than 4" in a combined system where hydraulically calculated.

NFPA 14 7.6.3 says you /cannot/ go less 4" in a SPRINKLERED BUILDING where hydraulically calculated. Note that is does not say ANYTHING about it being a combined system..

NFPA 14 7.6.2 says you cannot got less than 6" in a combined system. PERIOD, end of story. No exceptions for hydraulic calculations.

See what I mean?

If NFPA 14-7.6.3 does not apply to a combined system, and 14-7.6.2 is more restrictive than NFPA 13, then I'm going with NFPA 14..

If it wouldn't hold up in court I'm not comfortable with it, so I think I'll stick with 6" minimum in combined systems..