CENWAT Flue Requirements & Pressure Relief

Question 1

What is the minimum horizontal distance a room-sealed flue terminal must be from an openable window or door?

Accepted Answer

300 mm

Answer

100 mm

Answer

1000 mm

Answer

50 mm

Question 2

What is the minimum height above a flat roof that a flue terminal must be positioned?

Accepted Answer

600 mm above the roof surface

Answer

100 mm

Answer

300 mm

Answer

1500 mm

Question 3

What colour must the outer casing of a flue pipe be to indicate it carries flue gases from gas appliances?

Accepted Answer

There is no mandatory colour — identification is by labelling and documentation

Answer

Yellow

Answer

Red

Answer

Blue

Question 4

What is the purpose of a flue draught diverter on an open-flued appliance?

Accepted Answer

To prevent down-draughts from extinguishing the pilot or burner and to dilute flue gases with room air

Answer

To increase flue draught

Answer

To reduce noise from the flue

Answer

To seal the flue when the appliance is not in use

Question 5

What is the maximum length of 100 mm diameter horizontal flue permitted on most domestic gas boilers without additional checks?

Accepted Answer

Typically up to the manufacturer's maximum stated equivalent length (often 2–3 m for standard kits)

Answer

10 m

Answer

50 m

Answer

There is no limit

Question 6

What is a concentric flue system?

Accepted Answer

A flue system where the combustion air duct surrounds the flue gas duct in the same fitting

Answer

A flue system with multiple separate pipes

Answer

A flue system for condensing boilers only

Answer

A flue system used exclusively for open-flued appliances