Mind your tap gaps

Recent arrivals at the domestic kitchen sink include taps with hoses/pull-out spouts, taps which fold into the sink below the work top level and ‘pull-down’ taps like those in commercial kitchens.

Kitchen taps with pull-out spouts, fold-down and pull-down styles may be attractive and user-friendly but they can be problematic.

The issue is they can all pose a risk to health through backflow because their outlets can be submerged in the sink contents – as well as dirty washing up water, the contents in the sink could include cleaning chemicals or pathogens from uncooked food.

It’s the installer’s duty to ensure any work they carry-out complies with regulations. These taps may not comply when connected directly to a mains water supply and so other arrangements must be made.

Need for an air-gap

The regulations require the supply to be protected from contamination by means of suitable backflow protection. The conventional approach is to provide a Type AUK3 tap gap (illustrated to the left); the minimum distance must be 20mm or twice the inlet diameter of the feed pipe to the tap, whichever is the greater.

Is there any other way? Yes – an alternative is to supply hot and cold water to taps via an elevated cistern with an air gap – the type AUK1 air-gap (interposed cistern). Booster pumps can increase flow, but need consent from the water supplier if delivering over 12 litres per minute.

‘Break tanks’ are also an effective way of providing adequate backflow protection. They must be installed to comply with the Regulations to protect water against contamination. However the taps may have minimum pressure requirements which may not be provided using this arrangement.

For a ‘break tank’ or interposed cistern, use an approved cistern and inlet valve with a close-fitting lid and a correctly installed warning pipe (overflow). Remember, for non-domestic properties, it’s a requirement to notify the local water supplier and obtain consent for the proposed installation in advance of starting work.

This advice is published by WRAS and was revised in 2015 (click here to view)

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WRAS news - Spring 2016