Appendix UK – 13
3.3 Discharge pipe arrangement
The tundish must be positioned away from any electrical devices.
The tundish must be installed so that it is visible to the occupants.
Figure 7.
3
4
5
6
1
2
600 mm maximum
300 mm minimum
The principal installation solution of the discharge pipe assembly.
Position Name
1 Safety device (for example, temperature relief valve)
2 Metal discharge pipe from safety device to tundish
3 Tundish
4 Discharge pipe from tundish, with continuous fall (1 in 200)
5 Discharge below fixed grating
6 Trapped gully
Sizing of copper discharge pipe (4) for common temperature relief valve outlet sizes
Valve
outlet
size
Minimum
size of dis-
charge pipe
(2)
Minimum size of
discharge pipe (4
from tundish)
Maximum resistance allowed,
expressed as a length of
straight pipe (that is, no
elbows or bends)
Resistance created by
each elbow or bend
G1/2 15 mm
22 mm Up to 9 m 0.8 m
28 mm Up to 18 m 1.0 m
35 mm Up to 27 m 1.4 m
G3/4 22 mm
28 mm Up to 9 m 1.0 m
35 mm Up to 18 m 1.4 m
42 mm Up to 27 m 1.7 m
G1 28 mm
35 mm Up to 9 m 1.4 m
42 mm Up to 18 m 1.7 m
54 mm Up to 27 m 2.3 m