Page 335 - The City and Guilds Textbook: Plumbing Book 1 for the Level 3 Apprenticeship (9189), Level 2 Technical Certificate (8202) and Level 2 Diploma (6035)

Chapter 5 Cold water systems

These can usually be supplied in six different forms:

1 Activated carbon filter: used to reduce taste and odour such as chlorine.
The carbon filter has a large surface area that attracts and absorbs organic
substances from the water. The carbon is usually in powder, granular or
block form.
2 Ion exchange: used to reduce limescale formation and other metal-ion
contaminants such as lead. It takes the form of tiny granules, which work
by replacing the mineral or contaminant ions with hydrogen ions. p Figure 5.116 Fitting a water filter
3 Sediment filter: designed to remove fine particles from the water. These
comprise a mesh through which the water passes, trapping the sediment.
The smaller the holes in the filter, the smaller the particles that can be
removed.
4 Reverse osmosis: these work under pressure to remove most of the
dissolved mineral content by passing the water through a very fine
membrane.
5 Distillation: removes the mineral content of the water by boiling it and
condensing the steam back to water vapour.
6 Disinfection: used to reduce the bacteria content and other micro-
organisms by either UV light or a very fine sediment filter (usually ceramic or
membrane).

Installation of cold water pipework
Many of the requirements for pipework installation are covered in Chapter 2,
Common processes and techniques. Here, we will look at those techniques
specific to cold water installations.

Choosing the right materials
Cold water supply in domestic dwellings, as we have already discussed, is
strictly regulated by the Water Supply (Water Fittings) Regulations. This
means that the choice of materials for cold water installations is limited to
the following.
● Copper tubes and fittings (refer back to Chapter 2, Common processes
and techniques) – copper has a proven record for cold water installations.
It is light, rigid, has many jointing techniques available and requires only
minimal clipping. It is highly resistant to corrosion and has a minimum
life, in ideal conditions, of 150 years. It does, however, take great skill to
fabricate and install it properly. There is a fire risk when using soldering
equipment and it requires many specialist tools to successfully complete
an installation.
● Polybutylene pipe and fittings (refer back to Chapter 2, Common processes
and techniques) – manufacturers state that PB-1 has a life expectancy of
50 years. It is light and extremely flexible, and requires regular clipping
when fixed on the surface. It is easier to install and can be cabled through
joists easily and quickly. Push-fit joints make installation quicker and so
installation time can be reduced by 40 per cent with no fire risk. Testing
techniques are more complicated and time consuming than for copper tube.

323

9781510416482.indb 323 29/03/19 8:59 PM