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Water Storage Tanks

Standard of construction for sprinkler tanks

It is essential that the water storage tank is of robust construction and is designed and constructed to need little maintenance or servicing. Sprinkler water storage tanks are built to a high standard that will provide a 10-year service

life a requirement for LPCB listing for tanks for systems which require a „Superior‟ water supply) without there being any need for drainage and cleaning.

Where sprinkler systems are designed to the LPC Rules for Automatic Sprinkler Installations incorporating BE EN 12845:2009 the most commonly used water storage tanks have LPCB approval. LPCB listed tanks must comply with the rigorous manufacturing and test standard LPS 1276.

Type „A‟ tanks with a 15 year maintenance free period can still be provided for contracts designed to the now obsolete BS 5306 Part 2:1990

A list of LPCB-approved tanks can be found in the LPCB„Red Book‟ and on their website. These tanks come in sizes from 5m³ up to 1300m³ depending on the hazard category of the sprinkler system. If a larger capacity is required a combination of approved tanks can be used.

The relevant sections of the LPC Rules for Automatic Sprinkler Installations incorporating BS EN 12845: 2009 that apply to water storage tanks for sprinklers are:

  • TB 203 Care and maintenance of automatic sprinkler systems
  • TB 204 Sprinkler system grading
  • TB 209 ESFR sprinkler protection
  • TB 218 Water supply diagrams
    • TB 221 Sprinkler in schools
    • TB 224 Water storage tanks (cisterns)
    • TB 229 Variations to BS EN 12845 rules
    • TB 233 Water supplies for life safety systems

Sprinkler tanks are also listed by the US insurers‟ certification body UL and by the industrial insurer FM Global for use on specified sites. For contracts designed to NFPA 13 (US National Fire Protection Association Codes) either an FM or LPCB

Types of Tanks Used to Store Water

Cylindrical Galvanised Steel or Aluminium Tanks This type of water storage tank is the most common type used for sprinkler systems. Construction is by galvanized steel or aluminium sheets that are bolted together to form a cylinder. A mastic seal is applied between each metal sheet or a butyl rubber or EDPM liner is fitted. These tanks are usually installed close to the protected premises on a prepared concrete base or occasionally inside the protected premises.

Galvanised Pressed Steel Panel Tanks

These tanks are constructed using square steel panels that are bolted together to form a cube shape to suit the space available. They can be installed inside or outside the premises. This picture shows the access ladder, ball valve housing and tank infill pipe.

Profiled Galvanised Steel Panel Tanks

These tanks are constructed using square steel panels that are bolted together to form a cube shape to suit the space available. They can be installed inside or outside the premises. This picture shows the access ladder, ball valve housing and tank infill pipe.

Profiled Galvanised Steel Panel Tanks

The panels for this type of tank are curved and individually bolted to upright stanchions. They can be installed inside or outside the premises.

Moulded GRP Panel Tanks

These tanks are formed by bolting together square GRP panels to form a cube to suit the space available. They can be installed inside or outside the premises. This picture shows the service main infill to the two ball valves (black pipes), two grey drain pipes and a water level switch (white pipe)

Corrugated Galvanized Steel Panel Tanks

The panels are bolted together to form a cube shape to suit the space available. They can be installed inside or outside the premises.

pic-4Gravity Tanks

Can be any of the above tanks installed high up in a tall building, on a hill or on a separate high level platform. Depending on the tank‟s elevation, the „static‟ pressure or „head‟ can sometimes be sufficient to supply the needs of the sprinkler system.

Pressure Tanks

This is a cylindrical steel pressure vessel which is filled to two thirds capacity with water and one third with air under pressure. In the event of a fire the pressurised air expels the water and delivers it to the sprinkler system. This type of water supply can be found on older sprinkler installations and is no longer commonly installed on new sprinkler systems.

Concrete tanks

On sites where there is insufficient space above ground or because of planning restrictions an underground tank can be constructed from concrete. The standard for the construction of such tanks is BS 8007.

Retrofit Concrete Tanks

Where a concrete structure that will bear the load of the stored water exists on a site, it may be possible to provide a

fire sprinkler water storage tank in a retro-fit situation. The concrete structure can be lined with a butyl rubber or EDPM internal membrane similar to that used in steel tanks. The lining material can be either pre-fabricated and taken to site in one piece and installed, or fabricated on site to suit a particular tank, through specialist hot vulcanising or welding techniques.

Single-piece GRP Underground Tanks

These are a single piece domed end cylindrical tanks which is installed below ground, strapped to a concrete base or with a concrete surround. At present, there are no tanks of this type listed by the LPCB.

pic-1Other Acceptable Sources of Water

Provided adequate capacity exists, swimming pools, lakes, canals and rivers can be used as the water source for a sprinkler system provided the supply and availability is guaranteed. Because these sources may contain foreign matter in suspension it is necessary to fit a strainer (and sometimes filters) to minimise the risk of clogging pumps and the sprinkler pipes.

Underground Tanks and Pump Houses

Underground tanks or pump houses may sometimes be the only option but these are subject to some constraints and problems may occur in respect of dampness as well as issues of access. It is strongly advised that the insurers‟ views be sought before proceeding with such an installation. There is useful information on working in confined spaces in Part 3 (Supplementary Information) of the LPC Rules.