9
GENEVA
UNVENTED WATER HEATER
Figure 3 - Typical discharge pipe arrangement
Table 1 - Sizing of copper discharge pipe “D2” for common temperature relief valve
outlet sizes
Valve outlet
size
(diameter,
inches)
Min. size of
discharge
pipe D1 (mm)
Min. size of
discharge
pipe D2 (mm)
Max. resistance
allowed (length of
straight pipe - no
elbows / bends (m)
Resistance
created by each
elbow or bend (m)
G 1/2
15
22
28
35
up to 9
up to 18
up to 27
0.8
1.0
1.4
G 3/4
22
28
35
42
up to 9
up to 18
up to 27
1.0
1.4
1.7
G1
28
35
42
54
up to 9
up to 18
up to 27
1.4
1.7
2.3
