Hot Water

Question 1

What is a direct hot water system?

Answer 1

A system where the water is heated directly by a heat source like a boiler or immersion heater.

Question 2

What is an indirect hot water system?

Answer 2

A system where water is heated via a heat exchanger using water from a boiler.

Question 3

What is an open vented system?

Answer 3

A system with a vent pipe open to the atmosphere, fed by a cold feed cistern.

Question 4

What is an unvented hot water system?

Answer 4

A mains-fed system that is sealed and does not have a vent pipe.

Question 5

What is an instantaneous water heater?

Answer 5

A heater that warms water instantly on demand without storing it.

Question 6

What is a thermal store?

Answer 6

A vessel that stores hot water to indirectly heat mains cold water through internal coils.

Question 7

How does a combination boiler work?

Answer 7

It provides both central heating and instantaneous hot water using a plate heat exchanger.

Question 8

What is a single feed self-venting cylinder?

Answer 8

An older system using air separation inside the cylinder; now obsolete.

Question 9

What is the typical pipe size for a gravity primary flow?

Answer 9

28mm.

Question 10

What size is commonly used for a pumped primary flow?

Answer 10

22mm.

Question 11

Where should the open vent pipe terminate?

Answer 11

Over the feed cistern but above the water line.

Question 12

What is the purpose of a feed and expansion cistern?

Answer 12

To supply cold water to the system and accommodate water expansion.

Question 13

What does ‘stratification’ refer to in hot water cylinders?

Answer 13

The natural layering of water temperatures within a cylinder.

Question 14

What is a suitable material for hot water cylinders to prevent rust?

Answer 14

Copper, bronze, or stainless steel.

Question 15

What is the typical size of domestic hot water draw-off pipes?

Answer 15

22mm for baths, 15mm for basins.

Question 16

Why is it important to insulate hot water pipework?

Answer 16

To prevent heat loss and reduce energy waste.

Question 17

What must be fitted on the hot water feed to the cylinder?

Answer 17

A gate valve for isolation.

Question 18

What type of pump is used for secondary circulation?

Answer 18

A bronze-bodied pump.

Question 19

What temperature should hot water be stored at to prevent legionella?

Answer 19

60°C.

Question 20

What is the use of a thermostatic mixing valve (TMV)?

Answer 20

To control water temperature and prevent scalding.

Question 21

What type of valve prevents backflow in a hot water system?

Answer 21

A single or double check valve.

Question 22

What type of hot water system requires two cisterns?

Answer 22

Double feed indirect system.

Question 23

What is a common cylinder size for domestic hot water?

Answer 23

900mm x 450mm, giving around 120 litres.

Question 24

What device prevents overheating in immersion heaters?

Answer 24

A high-limit thermostat or thermal cut-out.

Question 25

What can cause 'kettling' in hot water cylinders?

Answer 25

Limescale or sludge build-up in the heat exchanger.

Question 26

What must be done before replacing a hot water cylinder?

Answer 26

Isolate, drain, and disconnect services.

Question 27

How often should a gas-fired water heater be serviced?

Answer 27

Annually by a Gas Safe registered engineer.

Question 28

What is a sacrificial anode used for?

Answer 28

To protect the cylinder from internal corrosion.

Question 29

What can cause poor flow from a hot tap?

Answer 29

Blockages, airlocks, or scale build-up.

Question 30

What is a common problem with primatic cylinders?

Answer 30

Air bubble rupture leading to contamination.

Question 31

How is warm air distributed in a warm air system?

Answer 31

Through ducts and grilles in the floor, wall, or ceiling.

Question 32

What fuel is used in warm air systems?

Answer 32

Gas.

Question 33

How does an electric storage heater work?

Answer 33

It stores heat overnight and releases it during the day.

Question 34

What metering system supports electric storage heaters?

Answer 34

Dual tariff meters.

Question 35

What is the main disadvantage of electric storage heaters?

Answer 35

High running costs.

Question 36

Where is the heat for district heating generated?

Answer 36

From a central boiler plant.

Question 37

What mediums are used in district heating?

Answer 37

Hot water and steam.

Question 38

What is a district heating interface?

Answer 38

A unit that connects the central plant to individual properties.

Question 39

What should be done before filling a hot water system?

Answer 39

Visual inspection and ensuring all components are isolated.

Question 40

What should be flushed during commissioning?

Answer 40

All taps, outlets, and storage vessels.

Question 41

What temperature should an immersion heater be set to?

Answer 41

55–60°C.

Question 42

What is used to measure flow rate?

Answer 42

A flow cup or digital meter.

Question 43

What is back-syphonage and how is it prevented?

Answer 43

It’s water being drawn backwards into supply; prevented by check valves or air gaps.

Question 44

What document regulates hot water safety?

Answer 44

Building Regulations Part G.

Question 45

What document covers water fitting standards?

Answer 45

The Water Supply (Water Fittings) Regulations 1999.

Question 46

What is BS EN 806?

Answer 46

A set of British Standards for domestic water systems.

Question 47

What info should go on a maintenance record?

Answer 47

Engineer name, date, work done, components used, test results.

Question 48

What is permanent decommissioning?

Answer 48

Complete removal and capping off of a system.

Question 49

Why inform customers before isolation?

Answer 49

So they can make arrangements for water use.

Question 50

What must be done after decommissioning a cylinder?

Answer 50

Label and cap pipes, and update maintenance records.