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VALVE

OUTLET

SIZE

MINIMUM

SIZE OF

DISCHARGE

PIPE D1

MINIMUM SIZE OF

DISCHARGE PIPR

D2 FROM TUNDISH

MAXIMUM RESISTANCE

ALLOWED, EXPRESSED

AS A LENGTH OF

STRAIGHT PIPE (I.E. NO

ELBOWS OR BENDS)

RESISTANCE

CREATED BY

EACH ELBOW

OR BEND

G 1/2 15mm

22mm

28mm

35mm

UP TO 9M

UP TO 18M

UP TO 27M

0.8M

1.0M

1.4M

G 3/4 22mm

28mm

35mm

42mm

UP TO 9M

UP TO 18M

UP TO 27M

1.0M

1.4M

1.7M

G1 28mm

35mm

42mm

54mm

UP TO 9M

UP TO 18M

UP TO 27M

1.4M

1.7M

2.3M

Table 03: Sizing of copper discharge pipe (D2) for common temperature relief valve outlet sizes

NOTE: The table below 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.

600mm maximum

300mm

minimum

Safety device

(e.g. Temperature

relief valve)

Metal discharge pipe (D1) from

Temperature relief valve to tundish

Tundish

Discharge below

fixed grating

(Building Regulation

G3 section 3.61 gives

alternative points

of discharge)

Fixed grating

Trapped

gully

Discharge pipe (D2) from tundish,

with continuous fall. See Building

Regulation G3 section 3.56,

Table 1 and worked example

Figure 04: Typical discharge pipe arrangement (Extract from building regulation G3 guidance section 5.50)

Brand	Jet
Model	120i
Category	Water Heater
Language	English

Jet 120i User Manual

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Jet 120i Specifications