Unit 307 Session 6 Cold water systems

​COLD WATER SYSTEMS

​So far, we have looked at how water is collected, cleaned and distributed to houses and industry.

We will now move on to look at the cold water systems we install in dwellings.

​Domestic systems of cold water supply

​There are two basic systems of cold water used in domestic dwellings:

1 the direct system of cold water

2 the indirect system of cold water.

Open Ended

What do you think there are the differences between the 2 different systems of Cold water?

​The direct system of cold water supply

​With this system, all cold water taps are fed direct from the mains supply. This means that all taps are provided with a supply of drinking water.

A 15 mm rising main will be large enough to supply most cold water demands for a three- to four-bedroom house with all cold water outlets being supplied in 15 mm, including the bath

​​The direct system is the most commonly installed type of cold water system in domestic properties because its installation is cost effective and there is usually a relatively high-pressure supply available.

​Storage is required only for supplying cold water to the hot water cylinder via a 150-litre cistern. A feed cistern will not be necessary if the hot water is supplied via an instantaneous hot water heater or ‘combi’ boiler.

​If a hot water storage vessel is to be installed, then a 28 mm cold feed pipe is needed to the hot water storage vessel supplied from a 150-litre cold water feed cistern in the roof space

​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.

A 15 mm rising cold water main will be large enough to supply most cold water demands for a three- to four-bedroom house.

1. The kitchen sink should be supplied with water direct from the cold water main and 15 mm pipework is adequate for this.

2. The cold water storage cistern can also be supplied via 15 mm pipework.

3. A cold water distribution pipe (22 mm minimum) distributes cold water from the cistern to the washbasin, WC and bath.

4. The bath should be supplied from 22 mm pipework because of the lack of pressure, but all other appliances can effectively be supplied from 15 mm pipework.

5. A 28 mm (22 mm minimum) cold feed pipe is needed to supply the hot water storage vessel.

Multiple Choice

Which of these is an advantage of a direct cold water system?

• More structural support needed

• Cheaper to install

• Larger pipe sizes required

• Low pressure at outlets

Multiple Choice

Which of these is an advantage of a direct cold water system?

• Limited access to water

• No access to drinking water

• Drinking water at all fittings

• Drinking water in roof space

Multiple Choice

Which of these is an advantage of a direct cold water system?

• Smaller pipe sizes

• Larger pipe sizes

• Higher pressure

• Increased structural weight

Multiple Choice

What is a potential issue during times of peak demand in a direct cold water system?

• Increased pressure

• No change in pressure

• Pressure drop

• High pressure

Multiple Choice

What is a disadvantage if the mains are under repair in a direct cold water system?

• Low pressure

• No water supply

• Excessive pressure

• Limited access to taps

Multiple Choice

What is an advantage of an indirect system regarding water hammer and noise?

• Increased risk of water hammer

• Only noisy at night

• Reduced risk of water hammer and noise

• Greater pressure fluctuations

Multiple Choice

What is a benefit of an indirect system during mains failure?

• increased pressure

• Reduced pressure

• Reserve supply available

• Increased risk of backflow

Multiple Choice

In an indirect system, what is a potential risk associated with the roof space during cold weather?

• Increased heat to the water

• Risk of frost damage

• Reduced risk of frost damage

• No impact on frost damage

Multiple Choice

How does an indirect system impact the overall installation cost compared to a direct system?

• Reduced cost

• No impact on cost

• Increased cost

• Cost savings

Multiple Choice

What is a potential drawback of an indirect system in terms of pressure?

• Increased pressure

• No impact on pressure

• Reduced pressure

• Constant pressure

Multiple Choice

What type of cold water system is shown in the picture?

• Direct

• In-direct

Multiple Choice

What type of cold water system is shown in the picture?

• Direct

• In-direct

Multiple Choice

What type of cold water system is shown in the picture?

• Direct

• In-direct

Labelling

Label the diagram

Drag labels to their correct position on the image

230 litre Storage cistern

15mm rising main

22mm cold feed

22mm cold distribution