Source of Water Supply for Fire Fighting

By | December 1, 2020

Source of Water Supply for Fire Fighting:

Fire water refers to water that is used in firefighting and requires disposal. In many cases it is a highly polluting material and requires special care in its disposal.

In many firefighting situations, large quantities of water remain after the fire has been extinguished. The water contains materials present in the building and also contains dissolved and particulate materials from combustion processes and materials generated through quenching.

Fire water can be particularly polluting when the building or site being extinguished itself contains potentially polluting materials such as pesticides, organic and inorganic chemical reagents, fertilizers, etc. Certain types of premises including farms and the chemical industry pose special risks because of the types of materials present.

Using natural resources for hydrant.

Premises containing quantities of plastics can also cause severe problems because of the taste and odor imparted to the fire water. Releasing contaminated fire water into a river or other water source subsequently used to supply drinking water may render the untreated water supply unsuitable for drinking or food preparation.

Managing fire water frequently requires that the water be contained on site and then removed from site for specialized treatment. One of the recognized techniques is to contain the fire water in the drainage system using pneumatic bladders or lockable non-return valves which can be activated either automatically or manually. It needs to be reinforced that the ISO Fire Suppression Rating Schedule documents a minimum recognized available fire flow of 250 gpm for a duration of 2 hours for structural property.

This applies whether a structural fire risk is served by a municipal water supply system providing water for consumer use or not. In suburban and rural areas without water delivery from a municipal water system supplying fire hydrants, provisions need to be made by the jurisdictional fire department to transport water oat structural fires and other fire emergencies using fire pampers, pumper-tankers, and mobile water tankers.

To meet the minimum specified flow of 250 gpm for 2 hours or a higher flow as determined by the needed fire flow for specific fire risks, water supply sources need to be provided throughout a fire protection district or Graded Area.

Classification of sources :

These water supply sources are classified into two categories:

1) Natural water sources.

2) Developed water sources.

Natural Water Source Classifications &Developed Water Source Classifications are-

  • Lakes Rivers.
  • Ponds Cisterns.
  • Streams Driven wells.
  • Reservoirs Above ground storage tanks.
  • Streams Below ground storage tanks.
  • Rivers Elevated storage tanks.
  • Irrigation channels Swimming pools.
  • Domestic water systems.

The sources which are used to provide sufficient quantities of water for fire fighting. It may be fabricated as public water mains and water tanks (Fixed or mobile), or natural sources as rivers, lakes, wells and other similar.

Public water mains:

Distribution Pipelines forming a part of the water supply distribution network of any town or village which is pressurized under normal circumstances.

Public fire hydrants:

The hydrants which are fixed on branches distributed from public water mains for the purpose of fighting fires and to be used only by Civil Defense Authorities.

Private fire hydrants:

The hydrants which are recommended by the Civil Defense authorities for the protection private properties, it may be installed inside a building with special connections or outside around the building within the boundary of the property. These hydrants shall however be installed ana maintained at the owner’s cost.

Suction tanks:

Tanks which need water pumping system to provide adequate flow and pressure which will be suitable to extinguish the fire.

Water Supplies requirements:

  1. Most of water demanded for fire-fighting is taken from public wale mains, where these mains are available in the area with suitable capacities. Generally a water supply capable of providing a minimum of (1125 litre/min) at all times be required.
  2. In cases where the public water main supply does not meet the above requirement, each fire main should be fed from either an elevated reservoir or a suction tank or interconnected tanks having a minimum capacity of (45, 000) liters.
  3. The tank or tanks should be automatically supplied form any other source of water controlled by a ball valve (s) and the capacity of these mains together with the contents of the reservoir or tanks should be such as to maintain a flow of water capable of supplying three fire-fighting jets for 45 min, when water is supplying a total rate of (1125 litre/min).
  4. Tanks supplying water for domestic purposes should not be used as suction tanks unless arrangements have been made for these domestic supplies to be drawn off in such a manner that the requisite reserve of water is always preserved.

Reliability of Natural Water Supplies:

Impounded water supplies:

These supply sources consist of naturally developed ponds in low- lying areas that are accessible by all-weather roads, constructed ponds for fire protection, and small lakes that are natural or manmade with a retention dam at the out flow location.

NFPA 1142, 2002 edition, states that the quantity of water considered available for natural water supplies “is the minimum available during a drought with an average 50 year frequency that has been certified by a Professional Engineer or Hydrologist, or other similar qualified person.”

Flowing streams:

For all flowing streams, (i. e., rivers, streams, and creeks) NFPA 1142 states, “the quantity of water to be considered is the minimum rate of flow during a drought with an average 50 year frequency as obtained by a licensed Professional Engineer, Hydrologist, Geologist or similar qualified person.”

Municipal water supply systems:

Recognized fire hydrants on municipal water systems those hydrant tested to demonstrate a delivery of 250 gpm or more for 2 hours may be used to fill mobile water tankers or to relay water to protect areas beyond 1, 000 feet of the hydrant, This is a very important source of water supply when planning alternative water delivery program. Since, it may be one of the most reliable water sources for fire protection beyond water mains.

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