Installation Requirements
These fittings need to be installed in
accordance with the following Installation
Requirements and Notes (IRN) to ensure
they meet the requirements of the Water
Supply (Water Fittings) Regulations 1999
and the Scottish Byelaws 2004.
IRN R001: See text of entry for Installation
Requirements or Notes.
IRN R040 - Schedule 2-15 (1): 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 or
installations up to, and including, Fluid
Category 3.
If the fitting cannot be installed as indicated in
the table opposite it shall be installed as either
a or b below:
a: with an approved double check valve
assembly or some other no less
effective backflow prevention device
immediately upstream of the inlet.
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 fitting
(other than 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 20mm or
twice the diameter of the inlet pipe to the
fitting, which ever 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.
Size of tap or
combination fitting.
Vertical distance
of outlet above
spill-over level.
1. Not exceeding 1/2
in
20mm
2. Exceeding 1/2 in
but not exceeding
3/4 in
25mm
3. Exceeding 3/4 in
70mm
10
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