9
SIENA
Digital electronic water heater
WARNING -
The discharge will consist of scalding water and steam. Asphalt, roofing felt and non-
metallic rainwater goods may be damaged by such discharges.
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)
Minimum size of
discharge pipe D1
(mm)
Min. size of
discharge pipe D2
(mm)
Max. resistance
allowed, expressed
as 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
