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Cold Water Systems

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Aims and Objectives

• At the end of this session you will be able to:

• Explain the difference between a direct and indirect cold water and hot water system,

• Name all the pipework in a direct and indirect cold water system,

• Give the name of the valves which are designed to work with each system

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Task 1• Look at the two system drawing and;

• List the differences between them.

• Ascertain which appliance is always fed from the mains no matter what system is used and explain why you think this one appliance should always be fed from the mains.

• Make a list of advantages and disadvantages of each system and decide which one you would prefer in your own house and why.

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100 litre capacity

Bathroom Pillar Taps

Supply pipe

Open vent pipe

Hot distribution pipe

Cold Feed Pipe

Direct Cold Water system

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220l capacity

Bathroom Pillar Taps

Indirect Cold Water system

Open vent pipe

Hot distribution pipe

Cold Feed Pipe

Supply pipe

Cold distribution pipe

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• As you probably noticed from the drawing, an indirect cold water system is fed from a cistern,

• Therefore the pipework is filled ‘indirectly’ (through the cistern) from the mains.

• In a direct cold water system all outlets are filled ‘directly’ from the mains.

• (you can also have ‘combined’ systems which some outlets are fed from the mains and some from storage.)

• Which system do you think would generally have the highest pressure?

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• This is not to be mistaken with direct and indirect hot water systems,

• In the;• Direct hot water system,

the water is heated directly by the heat source (boiler or immersion heater)

• Indirect hot water system the water is heated indirectly from the heat source via a ‘secondary’ heat exchanger. (usually a coil in a cylinder)

• Again, we will look at this in greater detail in a later session

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Task 3

• Individually;

• Draw a direct system of cold water.

• When you finish name all pipes and consider the sizes of each pipe.

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litre capacity

Outside tap

Correctly draw a direct cold water system

You have 10 mins to complete this task

If you finish early label all pipe with their correct names and sizes also name all valves (inc. BS nos.)

Incoming main

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Task 4

• Individually;

• Draw an indirect system of cold water.

• When you finish name all pipes and consider the sizes of each pipe.

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litre capacity

Outside tap

Correctly draw an indirect cold water system

You have 10 mins to complete this task

If you finish early label all pipe with their correct names and sizes also name all valves (inc. BS nos.)

Incoming main

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• Generally indirect CW systems are used where there’s a low incoming water pressure

• Direct systems are generally used where the incoming pressure is high.

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• There are certain valves which are only supposed to be used in high pressure installation, and others which are only to be used for low pressure installations.

• (though many can be used on both high and low pressures)

• Screwdown stopvalves should only be used for high pressure installations

• Gatevalves should only be used for low pressure installations.

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• Gatevalves should only be fitted vertically or upside down

• Because otherwise the seat can be blocked with debris in the pipe

• There are other fullway valves which can be used if this is not possible

‘Fullway’ spherical plug valve

(can be used for high or low pressure)

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Task 5

• As we discussed previously anywhere where there is a risk of contamination we must provide backflow prevention methods.

• If a mixer valve was to be fitted under a sink what backflow prevention device must be used?

• What is the minimum backflow prevention allowed on a kitchen sink?

• If a bib tap was to be fitted outside what backflow prevention method is needed?

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Mixer Taps• There are two main types of mixer taps, one type

allows the water to mix in the body of the valve,• What sort of backflow prevention device would this need and why?

• And in the other the water doesn’t mix until it leaves the spout.

• What sort of backflow prevention device would this need and why?

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• ‘Single flow’ mixer taps should be fitted as shown below,

• Whereas twin flow taps do not need the single check valve.

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Bib Taps• A bib tap is a general

name for any tap in which the threads come out the ‘back’ of the tap,

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• Bibtaps would normally be screwed into a ‘backplate elbow’ if being used for an outside tap

• or over a Belfast or London Sink

• Explain which is Belfast/London sink• London no overflow.

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• If a temporary supply (stand pipe) is to be fitted on site a bib tap would be likely to be used for this.

• Which is Belfast/London sink?

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• Generally the type of tap used for outside taps is the bib tap.

• It is a requirement of the Water Regulations that outside taps must be fitted with a double check valve.

• This check valve can be incorporated into the tap rather than being fitted ‘in line’.

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Different styles of ‘Hose Union’ Bib Tap

With built in Double Check Valves and single Drain off Point

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• On an outside tap installation, it is also considered good practice, to fit a;

• service valve, and, • A drain off valve,• So it can be isolated and

drained during the winter months. (reducing the risk of frozen pipes bursting)

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Electrical insulator (plastic fitting).Protects system if tap is struck by lightning.(Not required if plastic pipework is used.)

Double check valve (with drain point).Not required if tap has built in valves.

Drain off cock

Back plate elbow

Hose union bib tap or a tap with built in check valves can be used instead of in-line check valve

Isolating valve

Pipe sleeve through wall with insulation

Typical Copper Installation Requirements

Main isolating valveand drain off cock to building.

15mm

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• Name the parts pointed out.

Mains supply pipe coming into the property

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Task 6Ask individual questions

• Explain the difference between a direct and indirect system of cold water.

• Explain the difference between a direct and indirect system of hot water.

• Which valve is designed to work only on low pressure pipework?

• Which system would be considered low pressure?• Which valve is designed to work only on high

pressure pipework? • Which system would be considered high

pressure?

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Task 7

• Using what we now know, go home and work out whether you have a direct or indirect cold water system.

• You could do this by checking the outlets of your CWSC, or,

• Another way would be by turning off the stopcock on the supply pipe and running the taps, if the supply runs for a short while then fades away it means it’s being fed from the mains, if you run it for a couple of mins and the flow rate hasn’t changed it means it’s probably fed from a cistern.

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Aims and Objectives

• At the end of this session you will be able to:

• Explain the difference between a direct and indirect cold water and hot water system,

• Name all the pipework in a direct and indirect cold water system,

• Give the name of the valves which are designed to work with each system