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General Requirements of firefighting water tanks | NFPA 22

Firefighting Water Tanks

Firefighting Water Tanks
Firefighting Water Tanks

Types of Tanks used in firefighting

Gravity Tank

A storage tank that uses elevation as a source of pressure, which might be capable of providing the necessary head pressure to operate a fire suppression system or used to provide water to a fire pump.

Suction Tank

A tank that provides water to a fire pump for which a minimal amount of head pressure is provided.

Break Tank

A tank providing suction to a fire pump whose capacity is less than the fire protection demand (flow rate times flow duration).

Pressure Tank

A tank that uses air or some other gas under pressure as a means of expelling its contents.

Bladder Tank

A type of pressure tank containing air and water separated by a flexible membrane (bladder).

Firefighting Water Tank Material.

Firefighting tank can be fabricated using one of the following materials:
  • Steel
  • Wood
  • Concrete
  • Coated fabrics
  • Fiberglass-reinforced plastic tanks.

Sizing of firefighting water tank.

  • A tank shall be sized so that the stored supply plus reliable automatic refill shall meet the system demand for the design duration.
  • A break tank shall be sized for a minimum duration of 15 minutes with the fire pump operating at 150 percent of rated capacity.

Calculation of the net capacity of a firefighting tank.

For suction tanks:

the net capacity shall be the number of gallons between the inlet of the overflow and the level of the vortex plate.

For all tanks other than suction tanks:

the net capacity shall be the number of gallons between the inlet of the overflow and the discharge outlet.

Connections for Use Other Than for Fire Protection.

Connections for other than fire protection shall be approved, and Pipe used for other than fire protection purposes shall be entirely separate from fire-service pipes and shall extend to an elevation inside the tank above that required for fire protection.

Firefighting Water Tank Vent.

A vent pipe shall have a cross-sectional area equal to a minimum of one-half the area of the discharge pipes or fill pipe, whichever is the larger.

Filling of firefighting water tank:

  • The water supply shall be capable of filling the minimum required fire protection volume within the tank in a maximum of 8 hours.
  • The tank shall be kept filled, and the water level shall never be more than 4 in. (102 mm) below the designated fire service level.

Discharge pipe sizing of firefighting water tank.

The minimum discharge pipe sizing shall be based on the hydraulic demand of the systems attached to the tank but shall not be less than 6 in.

Firefighting Water Tank Overflow.

  • The overflow pipe shall have a capacity greater than the fill connection but shall not be less than 3 in. throughout.
  • The inlet of the overflow pipe shall be located at the top capacity line or high waterline.

Firefighting Water Tank Drain.

A drain pipe of at least 2 in. that is fitted with a controlling valve and a 1∕2 in. drip valve shall be connected into the tank discharge pipe near its base and on the tank side of all valves.

Anti-Vortex Plate Assembly.

  • The discharge outlet for every suction tank shall be equipped with an anti-vortex plate assembly.
  • For more information about the anti-vortex plate, its dimensions and requirements, please visit the link below:

References of the article:

NFPA 22 - 2018 edition (Standard for Water Tanks for Private Fire Protection).

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