Heatrae Sadia ELECTROMAX Installation & Servicing Instructions Manual page 18

MINIMUM
VALVE SIZE OF
OUTLET SIZE DISCHARGE
PIPE D1
G 1/2 15mm
G 3/4 22mm
G1 28mm
Table 1 Sizing of Copper Discharge Pipes (D2) for Common T&P Relief Valve Sizes
NOTE: The above table is based on copper tube. Plastic pipes may be of different bore and
resistance. Sizes and maximum lengths of plastic should be calculated using data prepared for
the type of pipe being used.
Safety device
(e.g. Temperature
relief valve)
600mm maximum
Discharge pipe (D2 from tundish,
with continuous fall. See Building
Regulation G3 section 3.55,
Table 4 and worked example
Diagram 11 - Schematic Discharge Pipe Arrangement
18 Installation & Servicing Instructions
MINIMUM SIZE
OF DISCHARGE
PIPR D2 FROM
TUNDISH
22mm
28mm
35mm
28mm
35mm
42mm
35mm
42mm
54mm
Metal discharge pipe (D1) from
Temperature relief valve to tundish
Tundish
300mm
minimum
MAXIMUM RESISTANCE
ALLOWED, EXPRESSED
AS A LENGTH OF
STRAIGHT PIPE
UP TO 9M
UP TO 18M
UP TO 27M
UP TO 9M
UP TO 18M
UP TO 27M
UP TO 9M
UP TO 18M
UP TO 27M
G3 section 3.61 gives
RESISTANCE
CREATED BY
EACH ELBOW OR
BEND
0.8M
1.0M
1.4M
1.0M
1.4M
1.7M
1.4M
1.7M
2.3M
Discharge below
xed grating
(Building Regulation
alternative points
of discharge)
Fixed grating
Trapped
gully