Pipe installation
GENERAL
NOTE
Pipe installation must be carried out in accord-
ance with current norms and directives
NOTE
This installation is subject to building regulation
approval, notify the local Authority of intention
to install.
NOTE
Use only manufacturer’s recommended replace-
ment parts.
Waste water from safety valves is led via an unpressur-
ised overflow pipe to the drain, so hot water splashes
cannot cause harm.
The mouth of the overflow pipe must be visible and not
placed close to electrical components. In addition, the
mouth of the overflow pipe (tundish), drain valves and
motorised valves should also be positioned well away
from all electrical components. This is the only permitted
use of unpressurised overflow pipes. Overflow pipes
from tundish (WM1) connected to the expansion relief
valve (FL1) must also be connected to the drain in the
same way.
The connection for the T&P valve (XL29) must not be
used for any other purpose. Valves may not be posi-
tioned between the T&P valve (FL5) and the water
heater.
Overflow pipes from tundish must be routed with a fall
and be at least 300 mm long, before bends or angles in
the pipework (see image) and must also be frost-proof.
Matal discharge pipe
from tundish, with
continous fall.
Min. 300 mm
Tundish
Safety device
(e.g. temperature
relief valve)
Metal discharge pipe
from temperature relief
valve to tundish
Possible
wall
Discharge
below fixed
grating
Fixed
grating
Trapped
gulley
Max 600 mm
NOTE
The expansion vessel accomodates expansion
that results from heating the water inside the
unit. The expansion vessel must be connected
between the expansion valve and the cylinder.
The location of the expansion vessel should
allow access to recharge the pressure as and
when necessary.
Resistance created by
each elbow or bend
Maximum resistance
allowed, expressed as
a lenght of straight
pipe (i.e. no elbows or
bends)
Minimum size of dis-
charge pipe from tun-
dish
Minimum size of dis-
charge pipe
Valve outlet size
0.8 mm
up to 9 m
22 mm
15 mm
G1/2
1.0 mm
up to 18 m
28 mm
15 mm
G1/2
1.4 mm
up to 27 m
35 mm
15 mm
G1/2
1.0 mm
up to 9 m
28 mm
22 mm
<G3>/4
1.4 mm
up to 18 m
35 mm
22 mm
<G3>/4
1.7 mm
up to 27 m
42 mm
22 mm
<G3>/4
1.4 mm
up to 9 m
35 mm
28 mm
G1
1.7 mm
up to 18 m
42 mm
28 mm
G1
2.3 mm
up to 27 m
54 mm
28 mm
G1
Table sizing of copper discharge pipe for common temperature relief valve outlet sizes.
15
Chapter 3 | For the Installer
NIBE VPB S/ VPBS S
