The ATCM Cisterns and tanks – as time goes by

The ATCM, Cisterns, tanks

In a traditional industry such as water engineering and supply one might think nothing much changes when viewed from a consumer aspect. Water still flows out of the tap on demand.

However the last ten years have seen considerable activity behind the scenes, resulting in a safer, more efficient water product.

The ATCM and its members have played their part in several ways, from drafting British and European cistern product standards to the dissemination and adoption of these advances. They have delivered value-for-money products and provided practical guidance on product application and design, encompassing the requirements of the new Water Regulations.

BS 7491, Parts 1 to 3 (GRP Cisterns for Cold Water) was published in the early 90’s only to be superseded in 2001 by European Standard BS EN 13280, encompassing in one document both One Piece and Sectional GRP cistern products.

At the instigation of the ATCM and in partnership with the Water Regulation Advisory Scheme a WRAS Information and Guidance Note (IGN) was published in December 2003. The document offers a simplified and unified route through the Regulations related to ‘backflow’. See below for a link to the Note.

Elements within the Regulations still give rise to questions namely: Is it allowable to screen Type ‘AB Weir Spill Slots’ and is it a requirement to insulate all water tanks whose purpose is the containment of wholesome water?

Type ‘AB’ Air Gaps

Regulations require that the slot opening is ‘unrestricted’. Category 5 fluids present a serious health hazard and an open weir slot is appropriate as further contamination of a tank's content is of no concern. Industrial cisterns, butchery and meat trades, laboratories, grey water recycling systems are some listed examples.

Industrial cisterns with potable-standard contents, such as food processing and soft drinks factories, have different requirements. The Regulations state this to be a Fluid Category 5 risk and Type ‘AA’ or Type ‘AB’ protection must be installed. The only practical course of action for a Type ‘AB’ is to appropriately screen the open spill slot. The WRAS IGN publication offers guidance on this.

The insulation question

The ATCM, Cisterns, tanks

The Regulation Schedule 2-16(4c) advises: “Every storage cistern shall be fitted with thermal insulation to minimise freezing or undue warming”. The European Drinking Water Directive advises a 25oC maximum. The UK adopted a more conservative 20oC to take it below the level at which legionella bacteria can multiply. For cisterns in domestic household lofts, no statutory or advisory insulating properties or performance are provided.

Larger tanks may be in a different category dependent on their shape and holding capacity. Environmental conditions do not have such a significant effect on larger cisterns and tanks. However the general recommendation is that all cisterns and tanks containing wholesome water be insulated against the influences of environmental conditions.


An ATCM/ Water Regulation Advisory Scheme (WRAS) Information and Guidance Note, written as a practical guide, will provide in detail the requirements for cold water tanks and cisterns. View link: https://www.wras.co.uk/downloads/public_area/publications/general/ign9-04-04-cisterns-issue2.pdf/

Further information of the purpose and objectives of the ATCM is available at the link below. Note: The above information is advisory only.


Neil Weston – Chairman

Call us today! 0118 380 1980

Email: chairman@atcmtanks.org.uk

Website: see link below

For more information on this story, click here: December 2019, 05
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