Installation manual

13 ©ESP Ltd. Sept 2008
G3 GUIDANCE SECTION 4.10
The discharge pipe (D1) from the vessel up to and including the tundish is
generally supplied by the manufacturer of the hot water storage system. Where
otherwise, the installation should include the discharge pipe(s) (D1) from the
safety device(s). In either case the tundish should be vertical, located in the
same space as the unvented hot water storage system and be fitted as close as
possible and within 500mm of the safety device e.g. the TPRV.
The discharge pipe (D2) from the tundish should terminate in a safe place
where there is no risk to persons in the vicinity of the discharge, preferably be
of metal and:
a. be at least one pipe size larger than the nominal outlet size of the safety de-
vice unless its total equivalent hydraulic resistance exceeds that of a straight
pipe 9m long i.e. discharge pipes between 9m and 18m equivalent resistance
length should be at least two sizes larger than the nominal outlet size of the
safety device, between 18 and 27m at least 3 sizes larger , and so on. Bends
must be taken into account in calculating the flow resistance. Refer to Dia-
gram 7 and Table 1 below.
An alternative approach for sizing discharge pipes would be to follow BS
6700:1987 Specification for design, installation, testing and maintenance of
services supplying water for domestic use within buildings and their curti-
lages, Appendix E, section E2 and table 21.
b. have a vertical section of pipe at least 300mm long below the tundish before
any elbows or bends in the pipe work.
c. be installed with a continuous fall, and in a frost free environment.
d. have discharges visible at both the tundish and the final point of dicharge,
but where this is not possible or is practically difficult there should be clear
visibility at one or other of these locations.
Examples of acceptable discharge arrangements are:
i. ideally below a fixed grating and above the water seal in a trapped gully.
ii. downward discharges at low level; i.e. up to 100mm above external sur-
faces such as car parks, hard standings, grassed areas etc. are acceptable
providing that where children may play or otherwise come into contact
with discharges a wire cage or similar guard is positioned to prevent con-
tact, whilst maintaining visibility.
iii. discharges at high level; e.g. into a metal hopper and metal down pipe
with the end of the discharge pipe clearly visible (tundish visible or not)
or onto a roof capable of withstanding high temperature discharges of wa-
ter and 3m from any plastics guttering system that would collect such dis-
charges (tundish visible).
iv. where a single pipe serves a number of discharges, such as in blocks of
flats, the number served should be limited to not more than 6 systems so
that any installation discharging can be traced reasonably easily. The sin-
gle common discharge pipe should be at least one pipe size larger than the
largest individual discharge pipe (D2) to be connected. If unvented hot
water storage systems are installed where discharges from safety devices
may not be apparent i.e. in dwellings occupied by blind, infirm or disabled
people, consideration should be given to the installation of an electroni-
cally operated device to warn when discharge takes place.
Note: The discharge will consist of very high temperature water and steam.
Asphalt, roofing felt and non-metallic rainwater goods may be damaged by
such discharges and you must take this in to account when fitting the unit.
Should such damage be caused, ESP will accept no liability for any conse-
quent damage caused.
4 . Installation 4 . Installation
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