Secondary Water Source for Fire Protection

[sia101]

We are working on 8 story retail/residential building 90,000SF each floor, 95 ft High from the fire department access.
Pressure at street level is available at 70 psi. One fire pump station is to supply entire sprinkler system and 7 standpipes. Problem here is the Project Architect has not seen the building would need a secondary water source to supply fire protection system.

City has required that water tank as the secondary on-site water supply, in addition to main supply from the city water.

Roof structural is not able to support the weight of water tank and the only places abailable for water tank placement for the building is on 1st floor and the basement.

Can anyone please let me know 1)how would supply line from water tank is sized 2) how would the supply line taps to main fire water supply.

Would water tank need its own Boost Pump Assembly to keep stored water pressure to city water supply pressure?

 

[stookeyfpe]

I'll start by assuming you are in an area that has a seismic design category (SDC) that mandates a secondary water supply and is located in the US. Is that the case? Also, is your SDC assigned as category C, D, E or F? If so, a secondary water supply is required.

See IFC 903.3.5.2 for the design criteria for the sprinkler system. Do not exclude the demand for hose stream, or the 30 minute time period.

Your architect missed a pretty significant code provision. Good luck in dealing with that...

 

[PEDARRIN2]

I have a similar design where I have to have a secondary supply.

My primary supply is an 8" water main which feeds a 30,000 gallon storage tank. The tank is the secondary supply.

It will hold enough water for the rated flow of my fire pump for the required duration (1000 gpm for 30 minutes in my case.) My tank is in the basement.

I sized my pump for neglible suction which would be the worst case if the water main was broken and the tank was being drawn down.

Hope that helps.

 

[FFP1]

Booster pump fed by the public supply and a fire pump fed by a properly sized suction tank (based on the system demands). One electric and one diesel would make the most sense.

 

[GrandmarkFP]

Quote "Do not exclude the demand for hose stream"

Also see NFPA-13 2002 edition. 11.2.3.1.3: Inside and outside hose allowance is not required to be stored in a water storage tank that supplies a fire sprinkler system only. In this case the NFPA-14 stand pipe hose demand will need to be stored but not the out side hose stream.