Storage for fire flow in a well tank

[MSU95]

I am completing the design of a well house on a project that originally had been designed without fire flow considerations. The previous design called for a 5000 gal tank. Where can I find, or can anyone tell me, what the storage requirement for fire flow demand is?

 

[BobPE]

check the ISO (Insurance Service Office). I would venture a guess that it will be in the range of 150 to 1500 gpm for 90 to 120 minutes....A lot more than 5000 gals.

BobPE

 

[BobPE]

opps, that 150 gpm should read 750 gpm, my bad...

BobPE

 

[KRSServices]

Fire flow storage should be at a minimum, the capacity required to sustain your fire flow for a duration period of 2.5 hours. The total storage for fire flow in the reservoir should be 50% (or less) of the toal storage. The balance of the capacity should be the Peak flow, 5 day demand, and other usage demands deemed necesary. The fire flow should be calculated on the worst case structure, ie. wood frame offices or residential. This is a guideline in Canada, but it is a very good rule of thumb too. KRS Services

http://www.krs-services.com

 

[BobPE]

KRSServices:
how did you arrive at that 50% figure while at the same time coming up with 2.5 hours? Just curious.....

BobPE

 

[KRSServices]

Actually, I was trying to provide the shortest reply in the smallest space. The 2.5 hour flow period is a guideline I follow, unless the buildding or fire codes prescribe a longer duration. The 50% storage was intended as another guideline. When all considerations have been taken into account, and depending on the reservoir servicing, in many facilities I have been involved with, I have not seen the fire storage exceed 50% of the total storage capacity. You are quite correct, when I first read the initial thread, I thought the total capacity (assuming residential) was woefully inadequate. However, not knowing the specifics of this small system or in a rural setting, if the peak storage is only 5,000 gals, then then fire capability is likely a pumper/tanker combionation and setting up of a portable reservoir is quite normal, so therefore I felt that 5,000 gals may be adequate be sufficient because the small system pumps (or aquifer) would likely not be able to pump anywhere near what a pumper truck requires (5,000 gal storage + 5,000 gal fire = 10,000 gal). The storage should be calculated properly and not my guess. KRS Services

http://www.krs-services.com

 

[Muggle]

JUST A THOUGHT HERE - BUT YOU WILL HAVE TO TREAT THE STORAGE WATER TO PREVENT ALGAE/BIOFILM GROWTH THAT CAN PLUG THE SPRINKLER HEADS. NORMALLY, THERE ARE STATE REQUIREMENTS FOR HOW OFTEN YOU AHVE TO DISCHARGE THE LINES/TANK TO PREVENT BIOFOULING, BUT THIS CAN BE A MAJOR DRAWBACK DEPENDING ON THE WATER/REFILL SOURCE. YOU SHOULD INCLUDE A UV OR OTHER TREATMENT SYSTEM (NOT OZONE IF THE PLUMBING IS METAL AND NO VENTILATION FOR THE TANK TO THE OUTSIDE) TO PREVENT BIOFOULING. SEEMS NIT PICKY - BUT THERE ARE LIABILITY ISSUES IF YOU DON'T ADDRESS IT.
DAVE

 

[quark]

As per our country codes the capacity of tank should be sufficient enough to supply the pump with two hours capacity. The water from the fire water tank is made to overflow into a tank of general usage thus reducing chances of stagnation.

Regards,

 

[MSU95]

Thank you all for your assistance.

Happy Holidays!

 

[RDK]

Also look in NFPA for fire fighting requirements.

I don't have the index with me but the web site is

http://www.nfpa.org

Storage requirements will obviously depend on fire flow requirements. I built two reservoirs at two different airports in the past couple of years that maintained 30 minutes fire flow capacity. (Same client, same risk engineer and virtually same design).

Again see the NFPA for guidance. They will most likely be referenced in the local building codes but check them as well in case they have a stricter requirement.
Rick Kitson MBA P.Eng

Construction Project Management
From conception to completion

http://www.kitsonengineering.com

 

[h2oman]

Is this a Resedential or a Commercial usage? have you checked with your local Fire Department? I suggest the following.

1. contact the local F.D. and ask them what thay need for fire flow. (ie: 1500 GPM for 2 Hrs = 180,000 Gal.)

2. add the system peek demand to this.

3. if the system will not use enough water to keep the water from stagnating, add a recurculating pump that pulls the water from the bottom of the tank and dumps it back in on the otherside in to the top of the tank. and if necessary add a disinfection booster to this line have it set up with a timer so the operator can adjust the amount of disinfectant that is added.

Jack Meister
AZ. OPP. grade IV
w_u_g_t@hotmail.com

 

[KRSServices]

CLearly, I think we have all been saying the same thing. Fire Storage will be a function of the requirement necessary fire demands, which can be obtained through the assistance of the local fire department. The next item to look at will be how your system can provide those demands, sustain or provide adequate flow (and pressure) for a fire demand. Perhaps some water modelling would help in this regard. Good luck. KRS Services

http://www.krs-services.com