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5
SYSTEM REQUIREMENTS - Domestic Hot Water
Domestic Hot Water Requirements (see note in Frame 14).
1. The domestic hot water service must be in accordance
with BS 5546 and BS 6700.
2. Refer to Table 1 for minimum and maximum working
pressures.
3. The boilers are suitable for connection to most types of
washing machine and dishwasher appliances.
4. When connecting to suitable showers, ensure that:
a.
The cold inlet to the boiler is fitted with an approved
anti-vacuum or syphon non-return valve.
b.
Hot and cold water supplies to the shower are of
equal pressure.
5. Hard Water Areas
Where the water hardness exceeds 200mg/litre, it is
recommended that a proprietary scale reducing device
is fitted into the boiler cold supply within the
requirements of the local water company.
Note.
Attention is drawn to the following extracts from the Building
Regulations 1991.
Regulation 11(1) (Giving of a building notice or deposit of
plans)
"Subject to the following provisions of this regulation, a
person who intends to carry out building work or to make a
material change of use shall:
a. Give to the local authority* a building notice in accordance
with 12; or
b. Deposit full plans with the local authority* in accordance
with regulation 13".
Regulation 12(4) (Particulars and plans where a building
notice is given)
".......a building notice shall be accompanied by a statement
which specifies:
*Attention is drawn to regulation 18 (supervision of building
work otherwise than by local authorities).
a. The name, make, model and type of hot water storage
system to be installed;
b. The name of the body, if any, which has approved or
certified that the system is capable of performing in a way
which satisfies the requirements of paragraph G3 of
Schedule 1;
c. The name of the body, if any, which has issued any current
registered operative identity card to the installer or
proposed installer of system."
Regulation 13(3) (Full plans)
"Full plans shall consist of:
a. Description of the proposed building work or material
change of use, and the plans, particulars and statements
required by paragraphs (1) to (4) of regulation 12: and...."
Note.
Bye-laws of the appropriate Water Undertake also apply.
Discharge Pipework
It is a requirement of Building Regulation G3 that any
discharge from an unvented system is conveyed to where it is
visible, but will not cause danger to persons in or about the
building. The tundish and discharge pipes should be fitted in
accordance with requirements and guidance notes of
Building Regulation G3. The G3 Requirements and Guidance
section 3.9 are reproduced in the following sections.
Information Sheet No.33 available from the British Board of
Agrement gives further advice on discharge pipe installation.
For discharge pipe arrangements not covered by G3
Guidance or BBA Info sheet No.33 advice should be sought
from either your local Building Control Officer or Ideal Stelrad
Group.
G3 Requirement
".....there shall be precautions..... to ensure that the hot water
istor system store condensing -
GENERAL
Installation and Servicing
discharged from safety devices is safely conveyed to where
it is visible but will not cause danger to persons in or about
the building."
G3 Guidance SECTION 3.9
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 temperature relief
valve.
Note.
The tundish is factory fitted during manufacture of the istor.
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 device unless its total equivalent
hydraulic resistance exceeds that of 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
An alternative approach for sizing discharger pipes would
be to follow BS 67100:1987 specification for design
installation, testing and maintenance of services
supplying water for domestic use within buildings and
their curtilages. Appendix E. section E2 and table 21.
b. Have a vertical section of at least 300mm long, below the
tundish before any elbows or bends in the pipework.
c. Be installed with a continuous fall.
d. Have discharges visible at both the tundish and the final
point of discharge but where this in 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 surfaces 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 contact 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 water and 3m from any plastic
guttering system that would collect such discharges
(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 single common discharge pipe should
be at least on 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
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