Graf UK’s large water tank in Essex

When it came to finding an underground firefighting water tank big enough for the job there was only one manufacturer main contractor Kier could go to – Graf UK.

The sustainable water management specialist, better known for its rainwater harvesting and wastewater treatment systems, supplied a super-sized 52,000-litre recycled plastic Carat XXL tank for an extension to Oak View School in Loughton, in Essex’s Golden Triangle.

And that’s not the biggest tank Graf can supply – its firefighting models can be designed to suit whatever the design capacity is on a scheme, utilising multiple adjoined tanks from the Carat XXL range or alternatively adapting its modular attenuation tank systems.

This tank was required because pressure from the local water main was insufficient which is one of the fire safety requirements of the 2010 Building Regulations. These allow an alternative source of water supply, in this case a static water tank with a minimum capacity of 45,000 litres.

The tank, complete with fire hose connection to BS336, was supplied by Graf distributor Southern Tanks and installed by specialist sub-contractor MA Divane complete with access turrets, maintenance and inspection ladder, and suction pipework, in just a couple of days.

Preparing the excavation, on a steep hill and in challenging conditions, and then finishing with EWS (Emergency Water Supply) signage approved by Essex Fire Brigade took a total of a couple of weeks.

The tank, believed by Mac to be the biggest he has worked with, was lowered into the excavation using slings supplied with it, onto a gravel base and backfilled with gravel instead of the more traditional concrete, to save time and therefore money on site. Graf

Mac McKenzie added: “Graf were a good company to work with and provided excellent follow-up support. They came down during the works and were very helpful.”

Oak View School is a SEN (Special Educational Needs) provider and the standalone extension on its former car park was required due to its success with students with moderate, severe and complex needs within the autistic spectrum.

The Carat XXL is the largest tank supplied by Graf, offering storage capacities previously only available with concrete and steel tank models. As well as firefighting water, its modular concept enables it to store and retain rainwater and function as a wastewater tank for local wastewater disposal. This, combined with its light weight, allows for more flexibility through design, planning and installation when compared with a concrete or steel tank option.

The light weight also saves time and money during installation as there is no need to lay gravel for truck and crane access – so often the case with concrete or steel tanks. It can be easily mobilised with a stationary crane or excavator, saving even more time and money.

Requiring an earth covering of just one metre, the ribbed construction of the Carat XXL means it can be driven over by a vehicle weighing up to 40 tonnes, and it can also be installed in groundwater up to its midway point. In appreciation of this quality, Graf offers the Carat XXL with up to a 25-year warranty.

About Catrin Jones

Assistant Editor

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