Page 274 - The City and Guilds Textbook: Plumbing Book 1 for the Level 3 Apprenticeship (9189), Level 2 Technical Certificate (8202) and Level 2 Diploma (6035)

The City & Guilds Textbook: Plumbing Book 1

100–150 litre storage cistern fitted with
BS 1212 part 2 float-operated valve
Spherical ball-type
service valve

No water pipes or cisterns in the roof space.
No risk of burst pipes due to freezing

22 mm or 28 mm cold feed WC cistern fitted with
to secondary hot water cylinder either a BS 1212 part 2 WC cistern fitted with either a BS 1212 part 2,
part 3 or part 4 float- part 3 or part 4 float-operated valve
22 mm or 28mm full-way gate valve operated valve
or lever-type spherical ball valve
Spherical ball-type Spherical ball-type
service valve service valve

15mm mains cold water to all appliances 15 mm mains cold water to all appliances
Appliance off the
cold water mains
Drain-off valves

Drain-off
valves

p Figure 5.23 The direct system of cold water p Figure 5.24 Direct cold water system with
supply combi boiler or instantaneous hot water heater

 Table 5.3 Advantages and disadvantages of the direct system of cold water supply
Advantages Disadvantages
Cheaper to install At times of peak demand, the pressure may drop
Drinking water at all fittings If the mains are under repair, the property has no water
Less pipework If there is a leak in the premises, there will be a great deal of
Less structural support required in roof space for the cold feed damage due to high pressure
cistern Can be noisy
More suitable for instantaneous showers, hose taps and mixer Greater risk of contamination to mains
fittings. Used in conjunction with a high-pressure (unvented) Greater wear on taps and valves
hot water supply More problems with water hammer
Smaller pipe sizes may be used in most cases Greater risk of condensation build-up on the pipework, which
Good pressure at all cold water outlets can easily be mistaken for a leak

The indirect system of cold water supply

With this system of cold water supply, only the kitchen sink and the cold water
storage cistern are fed directly from the mains cold water supply. The other appliances
are fed indirectly via the cold water storage cistern in the roof space. A large amount
of water will, therefore, need to be stored to supply both cold water and hot water to
appliances and fittings from a minimum of 230 litres of water stored in the cistern.
The system is designed to be used in low-pressure water areas where the mains
supply pipework is not capable of supplying the full requirement of the system. This
type of system also has a reserve of stored water for use in the event of mains failure.
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