IRN R040

Schedule 2-15 (1) 

The fitting, or outlet supplied by the fitting, shall be installed so that its outlet discharges above the spill-over level of any fixed appliance as indicated below: -

For backflow protection in domestic premises or installations up to, and including,  Fluid Category 3.

1.
Size of tap or combination fitting.
2.
Vertical distance of outlet above spill-over level.

1. not exceeding ½in

2. exceeding ½in but not exceeding ¾in

3. exceeding ¾in

20mm

25mm

70mm

If the fitting cannot be installed as indicated in the table it shall be installed: - 

a) with an approved double check valve assembly or some other no less effective backflow prevention device immediately upstream of the inlet; or

b) so that it draws water by gravity only from a cistern, or cylinder having a permanently open vent pipe, and the distributing pipe supplies no other fittings (other than a draining tap) at a lower level.

For backflow protection in premises or installations up to, and including Fluid Category 5. 

The vertical distance of the outlet above the spill-over level shall be not less than 20 mm or twice the diameter of the inlet pipe to the fitting, whichever is the greater.

If the fitting cannot be installed as indicated it shall be installed with a backflow prevention arrangement suitable for the Fluid Category.

Taps incorporating a hose union outlet

If the outlet of the tap assembly is designed to accommodate the attachment of a flexible hose and therefore potentially compromise the required AUK3 air gap, alternative Fluid Category 5 backflow protection is required, as the AUK3 air gap provided by the tap would not apply.