Page 313 - The City and Guilds Textbook: Plumbing Book 1 for the Level 3 Apprenticeship (9189), Level 2 Technical Certificate (8202) and Level 2 Diploma (6035)

Chapter 5 Cold water systems

In a domestic dwelling, AUK3 air gaps are most common at the kitchen sink
in the form of high-necked pillar taps, sink mixer taps or sink monobloc taps.
Sink mixers and monoblocs have a swivel spout. If a cleaners’ sink, Belfast sink
or London sink is being installed, it is important that any bib taps installed are
positioned so as to maintain an AUK3 air gap.

Control valve

Pipe interrupter

Not less than 150 mm minimum

Type DC In-line pipe interrupter
Suitable for protection against fluid category:
Back Back
- pressure 5 siphonage
Outlet
p Figure 5.73 Installation of a DC pipe interrupter

Taps and combination fittings discharging on non-domestic appliances and any
appliances in premises where a higher level of protection is required, such as
appliances in hospitals or other healthcare premises, require a type AUK3 tap gap.

DC pipe interrupter with a permanent
atmospheric vent

This refers to a non-mechanical backflow prevention device with a permanent
unrestricted air inlet, the device being installed so that the flow of water is in
a vertical downward direction. They are used where there is a threat of back
siphonage from a fluid category 5.

Type DC pipe interrupter, this device must be fitted with Normal direction
the lowest point of the air aperture not less than 150 mm of flow
above the free discharge or spill-over level of an appliance
and have no valve, flow restrictor or tap on its outlet.

Shroud
dust cover

Air inlet
apertures
Suitable for protection against fluid category:

- Back 5 Back Outlet
pressure
siphonage
p Figure 5.74 DC pipe interrupter

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