Fluid Category 5 Break Tank

Posted on 15th May 2016 at 10:55am

Cat 5 pump and tank setThe Water Supply (Water Fitting) Regulations 1999 provides five backflow prevention categories dependant on the risk level of the water use.

The regulations require back-flow prevention devices to prevent the water on the premises being drawn backward into the public drinking water supply. Backflow may occur in a number of situations, including burst pipes in the street or cross connection of the mains water supply with pressurised supplies on the premises. An assessment needs to be made of the potential dangers to health of the backflow – if the backflow water comes from a butcher’s shop it is more likely to be contaminated than a newsagent.

What is a Cat 5 break tank for?

Backflow needs to be prevented as the Water Companies primary obligation is to provide safe, clean drinking water (potable water) to the population. Water quality is  rigorously tested as it leaves the treatment plant, however if the water is subsequently contaminated it may cause widespread illness or disease.

Category 5 compliance is provided by a physical 'air-gap'. Water falls into the tank from the inlet valve. the height of the inlet valve above the maximum water level is laid down in the regulations. The laws of physics demonstrate that even in a back-flow situation, water cannot jump from the break-tank back into the mains water pipe. The critical provision of the air gap tank is the maximum water level. Therefore, the tanks have to have some form of weir that the water flows over to prevent the water level rising above its maximum. Type 'AA' airgaps use the top of the tank as the weir, type 'AB' tanks have a slot cut into the side of the tank for the water to pour over. 

In the legislation, fluid risk category 5 covers the following areas:

Fluid which represents a serious health hazard because of the concentration of pathogenic organisms, radioactive or very toxic substances, including any fluid which contains – 

faecal material or other human waste:

butchery or other animal waste: or

pathogens from any other source.  

A non-exhaustive list of examples of this include:

General:

Industrial cisterns

Non-domestic hose union taps

Permeable pipe other than domestic gardens, laid below or at ground level, with or without chemical additives

Medical:

Mortuary and embalming equipment

Commercial clothes washing plant in health care premises

Food processing:

Butchery and meat trades

Slaughterhouse equipment

Vegetable washing

Cat 5 break tanks

To provide category 5 compliance, Access Irrigation produce a Cat 5 break tank and pump set. The break tank has a category ‘AB’ air-gap and the pump re-pressurises the water. An auto start device on the pump brings the pump on when there is a water demand and will stop the pump when the demand ceases. The pump set is available with a range of Lowara pumps which can be matched to the flow and pressure requirements of the project.

Two units are available. The smaller unit has a storage tank that holds 91 litres of water and has a 1/2” BSP inlet thread and will handle an inflow of up to 1,200 l/h into the tank. The larger Cat 5 break tank also holds 500l of water, so the tank will hold a buffer of water is situations where demand is higher than the water inflow.

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Fluid Category 5 break tank
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Break tank and pump for fluid category 5 risks

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