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Contamination and Protection of Water Supplies: What Applications Require CAT 5 Tanks To Be Used

What is Category 5 (CAT 5) Water Supply?

A category 5 water supply poses the highest threat to public health and safety. Water is contaminated through backflow, the undesirable reversal of water flow within a plumbing system. This reversal can allow contaminated water or substances to flow back into the mains water supply.

What Is a Category 5 Fluid, How Bad Is It and What Are the Risks?

CAT 5 is characterised as a hazardous fluid due to its high concentration of pathogenic organisms, radioactive elements, or extremely toxic substances – this poses the highest threat to public health.

What Are the 5 Categories of Water?

The level of backflow risk associated with the fluid in a system is assessed using a five stage categorisation:

  • CAT 1: Drinking water
  • CAT 2: Water in CAT 1 with aesthetic changes in taste, odour, or appearance.
  • CAT 3: Water with a slight health hazard, which may contain low toxicity such as common disinfectants
  • CAT 4: Water with a significant health hazard which includes pesticides or environmental organisms
  • CAT 5: Water with a serious health hazard which includes very toxic substances, faecal or other human/animal waste

What Is a Cat 5 Water Tank?

TankBoost Cat 5 offers a solution for boosting water pressure and flow in an installation scenario where category 5 fluid is present. It features an air gap between the inlet and outlet, preventing any backflow of water from the tank or cistern into the mains water supply, making it suitable for commercial use. These air gaps are Type AB which satisfies the applicable requirements of Water Regulations for Category 5 systems.

What Are the Fluid Category 5 Water Regulations?

In the commercial or industrial properties, adherence to Fluid Category 5 water regulations is non-negotiable, given the potential ramifications of non-compliance on public health and regulatory compliance. To meet these stringent requirements, properties must implement robust water management systems to prevent backflow, such as the TankBoost Cat 5, when looking to boost water.

What Appliances Require Fluid Category 5 Protection?

Appliances in commercial or industry properties require CAT 5 backflow protection, as contamination of public water supply by backflow is a possibility and therefore a risk assessment is required. Some examples of appliances which need CAT 5 backflow protection include:


  • Industrial cisterns
  • Non-Domestic sinks, urinals
  • Grey water recycling systems


  • Dental/ medical practices
  • Mortuary and embalming equipment
  • Hospital dialysis machines

Food processing

  • Butchery and meat trades
  • Vegetable washing
  • Slaughterhouse equipment


  • Sewerage treatment cleansing
  • Drain cleaning
  • Water storage for firefighting

Commercial/ Agricultural

  • Irrigation with chemical additives
  • Insecticide or fertiliser applications
  • Farming
  • Garden Centres
  • Dog grooming parlours

How to Ensure You Comply with Water Regulations When Boosting Mains Water?

Using a TankBoost Cat 5 ensures that the water in the tank or cistern does not flow back into the mains supply. Appropriate backflow prevention measures must be implemented, as per the Water Supply Regulations (1999).

Regulations apply to all water fittings receiving a water supply as outlined by WaterRegsUK to safeguard public health. Installers must ensure a risk assessment is carried out and documented, and keep up-to-date with water regulations across all commercial and industrial properties.

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