The ATCM and the Water Regulations Advisory Scheme (WRAS) have jointly produced a WRAS Information and Guidance Note (IGN) entitled “Cold Water Storage Cisterns – Design Recommendations for Mains Supply Inlets”.
This is a practical guide to assist designers, isntallers and usersof water supply systems to ensure appropriate backflow protection (Air Gap) is provided within a cistern having mains water supply inlet/s for Water Regulation Fluid Categories 1 to 5.
See WRAS publication IGN No. 0-04-04 which is now available to download.
The tank panels for the sides and cover shall be insulated with a minimum of 25mm of foam and a resultant insulation value better than 0.06 W/m²/°C. The insulating material shall be manufactured using CFC and HCFC free blowing systems which have a GWP (Global Warming Potential) = 0.
All fasteners which are used wholly or partly internally within the tank shall be manufactured from grade 316 stainless steel, (grade 1.4401 in BS EN 10088-3:1995). External fasteners shall be galvanised to BS 7371- 6:1998 and external supports to BS EN ISO 1461:2009. Where stainless and galvanised components are connected, the metals shall be isolated from each other.
No internal structures shall be permitted where there is potential for water stagnation.
Where the tank capacity is greater than 1000 litres and is the sole water supply the capacity shall be split between two separate tanks (not a single tank with a partition).