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    Default Dwelling Sprinklers

    We have a recent construction boom (past 5 years or so) with many 2 and 3 story townhouse styles apts and condos. They are being equipped with "life safety sprinklers" consisting of small diameter CPVC risers (Blaze pipe is the brand name). Some have no FDC but some have a single 1-1/2" FDC. They are pressure tested to 200 PSI but nobody can recommend a good pump discharge pressure. At a commercial building our SOP says to maintain 150 PSI. Any ideas as to the peorper pump pressure?

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    A very good question (no such thing as a dumb one but some are better than others.....)

    I'm going to ask around about this one, but you can start by asking your local Code Enforcement or Fire Marshal's Office to see the building sprinkler plans. Contained within should be a set of hydraulic calculations, which will list the maximum flow and pressure requirement (calculated with all the friction losses.) It may be hard to understand, have a Fire Plans Examiner (your code official, fire marshal, or their designate) help you read them if necessary. You may even try calling the Fire Protection Engineer who designed the system (again contained within the building plans.)
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    FWDbuff, your right. The sprinkler drawings and the hydraulic calculations should contain the operating gallonage and pressure of the sprinklers. Given the size of the FDC I am going to say that the gallonage is about 80 gpm.
    Also, the local or state code enforcement officer should have signed off on the installation. They should have a copy of the drawings and calcs.

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    Quote Originally Posted by HEYVERN View Post
    FWDbuff, your right. The sprinkler drawings and the hydraulic calculations should contain the operating gallonage and pressure of the sprinklers. Given the size of the FDC I am going to say that the gallonage is about 80 gpm.
    Also, the local or state code enforcement officer should have signed off on the installation. They should have a copy of the drawings and calcs.
    I am a Code Enforcement Official, but unfortunately I have never done a (sfd) residential installation.
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    I'm going to go out on a limb and propose that any sprinkler system with any FDC should be supplied at 150 psi. I base this on the fact that someone somewhere hoped to make some of this stuff as "easy" on our end as possible. The diameter of the pipe and the connection may be related to the overall design flow, but does not necessarily require less pressure as in most cases smaller diameter equals higher pressures.

    As reference I found this in NFPA 13D (Sprinklers for 1 and 2 family dwellings):

    4.3.2 Where a fire department pumper connection is provided, the system shall pass a hydrostatic pressure test performed in accordance with NFPA 13, Standard for the Installation of Sprinkler Systems.

    From NFPA 13:
    24.2.1.1 Unless permitted by 24.2.1.2 through 24.2.1.6, all piping and attached appurtenances subjected to system working pressure shall be hydrostatically tested at 200 psi (13.8 bar) and shall maintain that pressure without loss for 2 hours.

    As I think it through, would't the heads require the same pressure as any other system? So like a nozzle they should require the same "nozzle pressure"?

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    Quote Originally Posted by RFDACM02 View Post
    I'm going to go out on a limb and propose that any sprinkler system with any FDC should be supplied at 150 psi. I base this on the fact that someone somewhere hoped to make some of this stuff as "easy" on our end as possible. The diameter of the pipe and the connection may be related to the overall design flow, but does not necessarily require less pressure as in most cases smaller diameter equals higher pressures.

    As reference I found this in NFPA 13D (Sprinklers for 1 and 2 family dwellings):

    4.3.2 Where a fire department pumper connection is provided, the system shall pass a hydrostatic pressure test performed in accordance with NFPA 13, Standard for the Installation of Sprinkler Systems.

    From NFPA 13:
    24.2.1.1 Unless permitted by 24.2.1.2 through 24.2.1.6, all piping and attached appurtenances subjected to system working pressure shall be hydrostatically tested at 200 psi (13.8 bar) and shall maintain that pressure without loss for 2 hours.

    As I think it through, would't the heads require the same pressure as any other system? So like a nozzle they should require the same "nozzle pressure"?
    As most know in addtion to 13 and 13D there's 13R "Standard for the Installation of Sprinkler Systems in Residential Occupancies up to and Including Four Stories in Height".

    In designing a system we use available city water supply so if the water pressure is 60 psi that is pretty much what we are going to use. I appreciate flow tests will give something similar to 60 static, 45 residual flowing 700 gpm but with 13R and 13D the amount of water required is so small it is a safe bet we will have available, and will use, something very close to the static pressure.

    13D requires the hydraulically most remove two sprinkler heads be calculated and with something like the Viking VK466 http://www.vikinggroupinc.com/databo...ial/091406.pdf the most water required for a flat ceiling would be 20 gpm from each sprinkler and that would be for spacing up to 10' off a wall and 20' apart. The end head pressure (meaning the pressure at the sprinkler head) would have to be 14.8 psi.

    For two sprinklers the actual demand would most likely be somewhere around 40.5 gpm.

    Installing something like this I would probably use 1" CPVC and with friction loss through the pipe, meter, backflow preventor and underground to the street I would expect our total pressure requirement would be around 30 psi at the point of FDC connection and 50 psi at the street to discharge the 40.5 gpm.

    All components are listed to 175 psi working pressure and everything is tested to 200 psi.

    In the event of a fire by connecting the pumper to the you can boost the pressure to 150 psi.

    If the system can deliver 40.5 gpm @ 30 psi we can calculate how much more water we can discharge from sprinklers by using the formula:

    k=q/p^.5 where k=constant q=gpm and p=psi

    In this case k=7.39

    Using the k-factor of 7.39 the amount of water discharged when the pumper delivers 150 psi would be:

    q=k*p^2 where k=constant q=gpm and p=psi

    In this case the two sprinklers would discharge a total of 90.5 gpm or between 45 and 46 gpm from each sprinkler.

    Is there much to gain by going to 175 psi?

    I don't think so.

    At 175 psi the total discharge would be 97.7 gpm or between 48 and 49 gpm from each sprinkler. An extra 25 psi only gives 7.2 gpm more or 3 1/2 gallons per head.

    Systems designed per NFPA 13D are not required to have fire department connections but systems designed per 13R are unless they are under 20 sprinklers in which case an FDC is not required.

    The major difference between a 13D and 13R systems in design criteria is a total of four sprinklers are required to be calculated in a 13R system as opposed to two in a 13D system.

    With four sprinklers the maximum demand is going to be somewhere between 80 and 85 gpm if the sprinklers are spaced 20' apart. If the heads are closer spaced, say 146x16', the minimum water requirement to each is reduced to 14 gpm. In the event of a 13D system the total demand would be between 28 gpm and 30 gpm while a 13R system would require somewhere between 56 and 60 gpm.

    I am not on the fire department, that's your business not mine, but I think 150 psi is a good number to shoot for.

    Addressing the 1 1/2" FDC connections I don't like em. 1 1/2" FDC's force fire departments to carry 2 1/2" x 1 1/2" hose adapters and in my mind the extra seconds or minute it would take could be critical. That's just my opinion which I am never shy at voicing.

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    Quote Originally Posted by nicetIV View Post

    Addressing the 1 1/2" FDC connections I don't like em. 1 1/2" FDC's force fire departments to carry 2 1/2" x 1 1/2" hose adapters and in my mind the extra seconds or minute it would take could be critical. That's just my opinion which I am never shy at voicing.
    These are very common adapters that any engine company should be equipped with, not to mention we all(99%) carry some sort of hose that uses 1.5" couplings, so as long as the flow doesn't exceed 200 gpm or more, they small attack lines could be used. Of course Life Safety Sprinklers are just that. Hopefully we're not relying on connecting to a 1.5" FDC to put out the fire. Unless your FD is fully staffed and right next door, the sprinklers should have done their job by the time the FD arrives, so the firefighters should probably just take a line in and finish up.

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