Dishwasher Air gap

“An air gap” within a dishwasher

Definition of a Break Tank:

A break tank is often referred to as a ‘Type A’ Air Gap but must not be confused with a ‘WRAS approved non-return valve’ as it provides an entirely different method of operation.

What is a Break Tank Dishwasher?

A Break tank may be fitted to a commercial dishwasher to prevent any possible back flow of dirty water (containing food debris, contaminates, bacteria etc). from the machine into the fresh water mains supply. They are installed into machines to ensure that there is no chance of contaminating fresh water supply.

“An air gap” within a dishwasher means a visible, unobstructed and complete physical air break between the lowest level of water discharge and the level of potentially contaminated fluid downstream (critical water level) within a cistern, vessel, fitting or appliance, hereinafter called a receptacle, that:

a. is not less than 20 mm or twice the internal diameter of the inlet pipe whichever is the greater; and

b. from which water discharges at not more than 15° from the vertical centreline of the water stream.

Follow the links below to get definitions of each of the recognised backflow prevention arrangements.

This article aims to provide advice to businesses assessing their requirement for a Break Tank (Type A Air Gap) when purchasing a commercial dishwasher or glass washer, such as care homes, nurseries, day care centers and hospitals.

How Does a Break Tank Dishwasher Work?

The break tank appliance works by feeding the incoming mains water supply into a separate tank first. This separate tank has an ‘air gap’ (a simple opening at the top that acts as an overflow).

From this tank, water is then fed into the dishwasher. This ensures that in the event of a fault in the dishwasher causing a backflow, contaminated water can only ever reach back into the break tank before it overflows through the ‘air gap’.

The result is that contaminated dish water can never enter the fresh water inlet.

Do I need A Break Tank (Type ‘A’ Air Gap)?

UK Water Board Regulations require commercial dishwashers to be fitted a Break Tank (Type ‘A’ Air Gap) wherever an installation is rated as being at category 5 level of risk or higher.

Generally, businesses rated at category 5 or higher will include any high-risk areas such as Schools, Care Homes, Nurseries or Hospitals where contamination of the water supply would be detrimental to hygiene and health.  It is the responsibility of a business to assess their own level of risk and comply with water board legislation.

Where is a Break Tank Located?

Machines listed with a Break Tank or ‘Type A Air Gap’ will have the break tank installed internally to the machine. This does not affect the machines performance, operation or dimensions.

Any dishwasher that does not have a break tank fitted as standard can have an external break tank unit fitted later, although units are generally bulky and take up additional space. Not having a break tank will not affect the machines performance. It is possible your plumbing already has a device in the system at an earlier point which does the same job.

What is a WRAS Approval?

Any water fitting, which when installed, will carry or receive water from the public mains water supply in the UK, must comply with the Water Supply (Water Fittings) Regulations or Scottish Byelaws.  These require that a water fitting should not cause waste, misuse, undue consumption or contamination of the water supply and must be ‘of an appropriate quality and standard’.

WRAS Approval is the easiest way to demonstrate compliance as it is granted directly by representatives of the water suppliers and is therefore accepted by every water supplier in the UK.

WRAS Product Approval: Whole products such as valves, boilers & showers undergo mechanical and water quality testing. This type of approval demonstrates full compliance with requirements of the regulations and byelaws, provided the fitting is installed according to any conditions given with the approval.

WRAS Material Approval: Non-metallic materials & components, such as rubber sheet material & ‘O’ rings, undergo testing only for their effects on water quality.  This type of approval demonstrates that the non-metallic material/component does not itself contaminate the water and therefore satisfies this particular requirement of regulations and byelaws.


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