Standpipe Design Question

[rfp2015]

Alright, I live in New York City & I have inspected many residential buildings that have gravity tanks and DO NOT HAVE FIREPUMPS.

15fls x 8 ft = 120
Lobby =12 ft
basement =12 ft
tank above roof = 15ft
(17) 16 inch slabs =272 inch / 12in = 22.6 ft
=181 ft
181 ft x 0.433psi = 78.373psi
water reserve is 15,000 Gpm

How does the system get its required pressure demand to meet NFPA 14 code in such a situation?, in fact NYC allows 65 psi.

I ask because once Hazen williams formula is used and equivalent pipe chart, psi will drop for (pipe fittings) elbows, OS&Y Valve, Check Valve, OS&Y Valve), Mech-Tee and the actual 2 1/2 house valve its self.

P.S. Thank you for your time.

 

[SprinklerDesigner2]

If I interpreted your question correctly the answer is it doesn't.

Not even close.

For 65 psi the bottom of the tank would have to be at least 65/.433=151 feet above the highest connection and that doesn't take into consideration any friction loss through pipe or valves.

 

[rfp2015]

yes I understand it doesn't get the required pressure, what im saying is I inspect alot of buildings with this going on.
A gravity tank feeding a single building or multiple buildings and there is no Firepump..

How would the system get the required pressure or is there something im missing?

 

[cdafd]

Maybe NY allows the fire truck to boost the system??

 

[cdafd]

http://www.nyc.gov/html/fdny/pdf/cof_study_material/s_13_citywide_standpipe_system.pdf

 

[rfp2015]

Thank you everyone for your thoughts

I have those certifications, I have read that book multiple times once I noticed this scenario at places I inspect...i suspect the buildings systems are grandfathered in...Im asking because I dont wanna make a stink about it at work and its something perfectly normal.

 

[cdafd]

Do you do the required flow tests???


If so how are you seeing the pressure and flow met???


Hydrostatic test (5 years) See Fire Department Code section 905.12.1
Flow test
Upon order of the commissioner, but at least once every 5 years, the standpipe system shall be subjected to a hydrostatic pressure test and a flow test to demonstrate its suitability for department use. These tests shall be conducted in compliance with the requirements of the rules and shall be conducted at the owner's risk, by his or her representative before a representative of the department.
(3 years) See Fire Department Code section 905.12.2
At least once every three (3) years, standpipe systems with pressure reducing devices installed shall be flow tested with a minimum actual flowing discharge of 250 gpm. These tests shall be conducted by a master fire suppression contractor who shall provide the Department five (5) business days notice of the date and time of the test. The Department may witness these tests at its discretion.

 

[rfp2015]

Yes I have performed many times. When the flow test is performed while FDNY inspector is present, they only ensure that the siamese connections are working with flow. During the hydro pressure test system is pumped usually 50psi above static pressure then system pressure is locked.

 

[stookeyfpe]

NYC is obviously amending NFPA 14 if they only require 65 PSI at some point in the system (I'm unsure based on your message). I can't speak as to the design requirements but knowing FDNY and their experience with high rise buildings, they probably have greater comfort in using the mobile pumping apparatus than using a fire pump inside the building. Removing the fire pump eliminates a potential failure mechanism because the Engine Chauffeur has a standardized maintenance schedule for the apparatus. Plus, FDNY has a variety of building construction rules because NYC Department of Buildings has been regulating them for over 150 years.

 

[rfp2015]

yes, NYC does allow 65 psi. The particular buildings im talking about do not have firepunps. The mention buildings only have gravity tanks. What I have noticed while performing inspections is that I get a base pressure of 75-125 psi ( standpipe base near riser control valve ) at various locations & I get a roof manifold pressure of about 5 - 25 psi ( 3 way manifold pressure gauge ). Does that mean NYC standpipes get 65 psi from NY Fire Department fire truck?

 

[TravisMack]

I guess so. Typically a high-rise should have an automatic standpipe but they may have options for manual standpipes.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

"Follow" us at

https://www.facebook.com/pages/MFP-Design-LLC/92218417692

 

[rfp2015]

Alright thanks, it was just something that has been on my mind lately.