Fire Water Tank

[waien]

Hi

Can fire water tank be combined with potable storage tank. In my situation it will be buried concerete tank, can some one qoute relevant codes in this regards from nfpa

 

[PEDARRIN2]

NFPA 22, 14.1.7 indicates the AHJ must be consulted prior to allowing water that is not for fire protection to be used.

But these types of tanks are used a lot.

One requirement (among many) is that any suction/drain from the tank for non fire protection water be at a level/elevation so it cannot drain the tank volume below what the requirements of the fire protection system needs.

 

[cdafd]

is this for a house or a commercial building??

 

[waien]

This is for a factory that is to produce Plastic Pallets, the production hall will be protected by CO2 system but the ware house shall be by sprinkler system and the location of this factory is in Saudi Arabia. Any idea about Saudi Code in this regards.

 

[stookeyfpe]

Carbon dioxide for the protection of the production hall? Good luck with that. You should consider sprinkler protection as that will offer a far more reliable, less expensive method of fire protection rather than CO2. I have no idea about Saudi Arabia codes.

 

[waien]

Yea that is specified by the equipment supplier as the machines are using diethermic oil which flows in closed cct within the machine @ 380C as such they have specified for CO2 protection

 

[DavidCR]

Yes, you can separate the water tank horizontally by the height of the potable water suction.

Other option is to divide the tank in chambers with a vertical wall and the filling system of each chamber may be independent or not, also considering that each chamber may overflow to the other side. In this case we like to provide independent filling systems (float valves) for both tank sections (using the same water source), since the refill flow for the potable water is very small and quite frecuent, compared to the high flow required for the fire tank that is not frecuent). Also it may be undesirable to oxigenate frecuently the fire water.

On C02. I´ve seen local aplication of CO2 in some process of a tire factory. With very effective protection on the most critical areas where solvents can get fire easily in a section of the production line. If total flooding is your case, God be with the people that work there, in that case I´d prefer to use sprinklers for general protection of the production hall.

 

[Kinemenematics]

with regards to code:

Have you tried checking the contract documents pertinent to your project? They should have a list of codes/standards there right?

with regards to ur original question:
"can some one qoute relevant codes in this regards from nfpa",

1. Do u need to know the construction requirements or the hydraulic requirements?
2. What else consumes water in ur fire-fighting system? Is it so simple that each room requires one kind of fire protection? Do you have passive fire protection systems in place? If your firewater tank is for sprinkler system only, check NFPA 13. Go look up NFPA's index

 

[waien]

Hi

The contract documents mostly here in saudi specifies NFPA,IBC.

Regarding the water storage tank for the fire protection system,in my view it should be combined with potable water tank and the suction of the potable water pump and fire protection pumps (both) should be from the bottom of the tank. The potable water pumps should be controlled via sensors mounted inside the tank at elevated levels (high level and low level) to stop the potable water from draining the whole tank and ensuring that a level of water below the low level sensor is always available and as such it will ensure that calculated amount of water is always available for the fire protection pumps i.e the water that is below the low level sensor.The advantage are as follows:

(A)If a separate water tank is maintained for fire protection the water quality keeps on getting degraded more so since the eventuality of fire breaking out in buildings is remote even on fifty years basis.This is quite a concern in area that have to maintain a water storage for FP system i.e no water mains supply available specially in middle east

(B)The cost of constructing single tank with combined volume will be lower than considering two independent tanks.

(C)The water quality in the tank is ensured by continuos flow of water from the tank i.e no stagnant water

(D) if the more obvious solution is sought i.e the potable water pumps suction from higher level and fire protection pumps from lower level this would create a stagnant volume of water below the suction of the potable water pumps. This stagnant volume of water would eventually get degraded and would be a constant source of pollution to the upper level water which is constant use for potable purposes.

The above design affords in my opinion best convergence of design simplicity + cost + Integrity + technology.

OVER TO HONOURABLE MEMBERS FOR DISSECTION AND CRITICISM.

 

[cry22]

It is taking forever to upload the Saudi Building Code for you on this site.
post your e-mail or dropbox to upload the Saudi Building code-Fire Protection for you.

 

[GeorgeMech]

your proposal is acceptable by NFPA related standard, however, it should be noted that in case you want this kind of set up, you need to consider the net effective capacity of the tank which can be calculated as per the most demanding system and as per the applicable duration, also, you should take into consideration about the separation / compartmentation of the fire water tank for maintenance purposes as required in NFPA 20 standard.

 

[stookeyfpe]

Hi

The contract documents mostly here in saudi specifies NFPA,IBC.

Regarding the water storage tank for the fire protection system,in my view it should be combined with potable water tank and the suction of the potable water pump and fire protection pumps (both) should be from the bottom of the tank. The potable water pumps should be controlled via sensors mounted inside the tank at elevated levels (high level and low level) to stop the potable water from draining the whole tank and ensuring that a level of water below the low level sensor is always available and as such it will ensure that calculated amount of water is always available for the fire protection pumps i.e the water that is below the low level sensor.The advantage are as follows:

(A)If a separate water tank is maintained for fire protection the water quality keeps on getting degraded more so since the eventuality of fire breaking out in buildings is remote even on fifty years basis.This is quite a concern in area that have to maintain a water storage for FP system i.e no water mains supply available specially in middle east

(B)The cost of constructing single tank with combined volume will be lower than considering two independent tanks.

(C)The water quality in the tank is ensured by continuos flow of water from the tank i.e no stagnant water

(D) if the more obvious solution is sought i.e the potable water pumps suction from higher level and fire protection pumps from lower level this would create a stagnant volume of water below the suction of the potable water pumps. This stagnant volume of water would eventually get degraded and would be a constant source of pollution to the upper level water which is constant use for potable purposes.

The above design affords in my opinion best convergence of design simplicity + cost + Integrity + technology.

OVER TO HONOURABLE MEMBERS FOR DISSECTION AND CRITICISM.[/b]

You are proposing to mix drinking water (safe, clean of bacteria) with fire protection water (can extinguish fire, contains all sorts of stuff a human is not intended to drink). The clients paying your salaries I seriously doubt will want suffering from projectile vomiting. You really need to be looking at a plumbing code.

 

[DavidCR]

You mention something in advantage (C) that is not always correct. I prefer "stagnant quality" water for fire, so as to have fire water with less risk to give corrosion or MIC problems. If you design a fire system that uses fresh water, or is used frecuently, I´d suggest to include especial cleaning and draining details and precautions that are not in the code.

 

[Duwe6]

" I prefer "stagnant quality" water for fire, so as to have fire water with less risk to give corrosion or MIC problems. If you design a fire system that uses fresh water, or is used frecuently, I´d suggest to include especial cleaning and draining details and precautions that are not in the code."

IIRC, that is SOP for any potable water tank. So, assuming this cleaning [and the usual epoxy/coal tar enamel paint], and a potable draw-off nozz located high enough in the tank that the 'heel' will always be sufficient for the firewater needs, I would build one combined tank. Just look at the extra cost of the paint & upkeep the lower, firewater section will need to meet potable requirements versus the cost savings of making one large tank instead of two medium ones.

 

[pipesnpumps]

A warehouse containing unexpanded plastic pellets is most likely going to require a large amount of water storage.. 150-250,000 US gallons.

What you will find is the potable water usage will likely not be enough to keep the water in the tank potable. There will not be enough potable water usage (flowrate) to keep a residual level of chlorine and low level of bacteria in the tank because there will be too much residence time.

Perhaps the water will be good enough to water the camels, or sprinkle the well manicured golf course, but I would look into potable water tank standards and determine the maximum allowable size of the tank for your minimum expected potable water usage, before persuing this idea further.



Real world knowledge doesn't fall out of the sky on a parachute, but rather is gained in small increments during moments of panic or curiosity.

 

[waien]

PEDARRIN2, pipesnpump,GeorgeMech, DavidCR i belive are getting it correctly the propesed tank utilisation for potable and Fire protection but with some reservaion anyway i do understand that residency time could be a factor specaily where large amount of storage is required with little usage for potable or oher uses (irrigation + cleaning ) but it seems the Idea would just be alright if residency of the avalbale water can be achieved.SAY 2 weeks max.

Further to that i would like to pose a very simple but pertinent question Say we have an underground storage tank only dedicated for Fire Protectio how long do we think the water will maintain it quality for Fire protection use? Think if their is no fire for 30 years or 50 years Dont we think that ALgae, Bacterial growth, etc could potentially be very harmful if sprayed indoor through sprinklers( The Algae could potentialy block the sprinklers) or Fire hoses and could also block the impeller of our pumps or at best trigger some emergency. I believe that thier should also be some code on the maximum residency time allowed for water in the Fire tanks or some other parameters to ensure against any potentail harmful or technical issues resulting form non utilised water for over 30 40 or 50 years.

waqqas

 

[stookeyfpe]

NFPA 22 states that the quality of the water must be evaluated. It offers no other guidance. NFPA 25 has no requirements for evaluation of water quality in existing fire protection water tanks. The quality of the water rests in the hands of the Engineer of Record. We can do nothing more for you.

 

[DavidCR]

"Stagnant" water is not a problem if proper design and NFPA22/25 (or any basic criteria of a water tank design/maintenance) are considered as Stookey mentioned. Im my experience (mostly from industrial installations) many clients find hard to accept that the stagnant water is better but when the system is finished, and they enjoy the advantages on maintenance and realibility, they find it was a not a bad thing. Maybe not in all cases of course.

I think only you have a real notion of your case, and you´ve seen some new points of view to consider.

On your question on algae/bacteria. I mean a simple fire water tank, not a 30-50 year abandonned tank, and how do you know they will grow better in stagnant water? Biological activity and debris problems depends on lots of other things.