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Water Tank Volume & Pipe Size

Water Tank Volume & Pipe Size

(OP)
Hi, a water tank will be put in the third level floor or slab. What must be the volume if gravity tank will be used so the pressure would be strong at 2nd floor and ground? It will be primarily as wet fire system. The tank won't be used for any other water applications since the building already has water line. Any website to compute for it as well as pipe size to ensure strong pressure? Also are gravity or pressurized water tank recommended for such kind of application? Thank you.

RE: Water Tank Volume & Pipe Size

For specifics on sizing tanks and piping for fire protection for a building, you would need to check with your local engineers who are actually in responsible charge of the system, that goes beyond the scope of free advice you can reasonably expect from a website. I assume the results are going to vary depending on size, use, and construction of the building, the building or fire code used, the location, etc.
That being said, I'm not so sure there is any requirement to furnish a tank in that situation. If you use a gravity tank, you'll have pretty minimal pressure available on the 3rd floor itself.
Where we more commonly see fire-protection tanks is where the local municipal supply is known to be limited, and there, they normally use gravity tanks plus diesel pumps.

RE: Water Tank Volume & Pipe Size

The volume of the tank has no direct influence on the pressure available on the 2nd floor. The pressure available at the 2nd floor nozzles depends on the height between the nozzles and the surface of the water in the tank. As the tank level drops the pressure in the nozzles will decrease, so the volume of the tank has an indirect effect on the pressure because the larger the tanks the slower the level will drop.

The pipe sizing depends on the flow rates you need. It is common to see pipe sizes change along the length of the reticulation system according to the number and position of the nozzles.

Having said all that, I agree with JStephen that if you are asking this type of question you should not be taking the responsibility for the design of a fire system. Get a local contractor who knows the regulations.

Katmar Software - AioFlo Pipe Hydraulics
http://katmarsoftware.com

"An undefined problem has an infinite number of solutions"

RE: Water Tank Volume & Pipe Size

Water tanks are also very heavy and generally can not just be placed on a floor that wasn't designed with the tank in mind.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Water Tank Volume & Pipe Size

The Volume of tank is not the effective point for the required pressure , the main issue is the height

RE: Water Tank Volume & Pipe Size

If the water tank is on the third floor, the pressure at the second floor will be about 8 psi when the tank is full (assuming a non-pressurized tank), which may be pretty much useless.

RE: Water Tank Volume & Pipe Size

If a water tank is sill sought out, then consider a pressurized water tank. One of the NFPA volumes has details on such tanks; it could be NFPA 13 but I am not certain.

RE: Water Tank Volume & Pipe Size

That is correct. Unless the tank is elevated on legs on the roof, you will never develop adequate water pressure below the tank.

You should be looking at a pressure tank or booster pump arrangement. The whole setup may be installed on the first floor.

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