Trade of Plumbing – Phase 2Module 2 – Unit 9

Module 2: Domestic Hot and Cold Water Services

Unit 9 – Valves and TapsDuration – 11 Hours

Trade of Plumbing – Phase 2Module 2 – Unit 9

In this module we learn how to:

Describe the types and application of valves and taps used in domestic plumbing systems.

Describe the operation and components of valves and taps. Replace stopcock, tap and ballvalve washers.

Trade of Plumbing – Phase 2Module 2 – Unit 9

Key Learning Points

RK Types and application of taps - pillar taps, mixer taps, monobloc taps, bib taps, etc.

RK Types and application of valves - stopcocks, gate valves, lever valves, drain cocks, etc.

RK Operation and components of taps and valves.RK Types, components and operation of float assisted

valves – high pressure, low pressure, diaphragm, portsmouth (BS), equilibrium.

RK Ball valve problems – water hammer, leaking, sticking, furring, cavitation.

SK Replacement of tap and valve washers.SK Identification of different types of washers, o rings etc.SK Use of tap re-seating tools.P Good working practice.P Problem solving.P Working independently.

Trade of Plumbing – Phase 2Module 2 – Unit 9

Valves and Taps

Valves and taps are devices designed to regulate, open or close the flow ofliquid or gas in a pipeline. Some of the more common valves and taps and their uses are as follows:

Stopcock - Used on incoming high pressure water mains. Gate valve - Used on low pressure pipework. Drain off cock - Used to drain pipework. Bib tap - A well mounted tap primarily used over sinks. Pillar tap - Used on sinks, wash hand basins and baths. Mixer taps - A tap which hot and cold water are delivered through a

common spout. Used in sinks. Plug cock - A quick closing valve used mainly on gas installations. Radiator valves - Used to control the flow of water to and from

radiators.

Trade of Plumbing – Phase 2Module 2 – Unit 9

Trade of Plumbing – Phase 2Module 2 – Unit 9

Trade of Plumbing – Phase 2Module 2 – Unit 9

Trade of Plumbing – Phase 2Module 2 – Unit 9

Trade of Plumbing – Phase 2Module 2 – Unit 9

Trade of Plumbing – Phase 2Module 2 – Unit 9

Trade of Plumbing – Phase 2Module 2 – Unit 9

Trade of Plumbing – Phase 2Module 2 – Unit 9

Repacking Glands on Radiator Valves

Trade of Plumbing – Phase 2Module 2 – Unit 9

Back SiphonageThe backflow of water by siphonic action from an appliance or storage cisterninto the pipe feeding it, thus contaminating the water supply. Any pipe on mains supply connected to appliances and cisterns must havesome means of backflow prevention. Where an outlet discharges, ensure anallowance is made for an air gap of at least that shown in the chart.

Internal Pipe Diameter Vertical distance (air gap) between outlet and highest possible water level

Up to 14mm15mm – 21mm22mm – 41mmOver 41mm

20mm25mm70mmTwice the internal bore of the inlet pipe

If a specified air gap cannot be achieved some other means of backflowprevention must be catered for. In the case of hose pipes and showerhoses connected to the mains supply a double check valve assembly orsimilar arrangement such as a check valve followed by an anti-vacuumvalve must be used.

Trade of Plumbing – Phase 2Module 2 – Unit 9

Draw Off Taps