Hydrants

Question 1

Two types of hydrant

Answer 1

Screw down hydrant

Sluice valve hydrant

Question 2

Inspection

Visual examination, paying particular attention to:

Answer 2

• Hydrant pits
• Frame
• Cover
• Surface surrounding the hydrant
• Frost valve
• Hydrant indication plate.

Question 3

Water hammer

Answer 3

Water passing through a pipe possesses both weight and velocity. If this flow is suddenly checked, the moving mass of water is instantly converted to pressure energy.
Since the pipe and its fittings must absorb this force, the sudden shock could burst or damage the main. This phenomenon is known as ‘water hammer’ and closing the hydrant down slowly can prevent it.

Question 4

Tuberculation

Answer 4

Tuberculation is a crust, which forms on the inside of the pipe due to bacteria or chemical reaction between water and metal.

Question 5

Crackling Jets

Answer 5

Air entering the pump somewhere in the system travels along the hose, is compressed at the jet end and leaves with explosive force (a crackling sound will be heard and the jet of water will be fragmented)

Question 6

Jet Reaction

Answer 6

When water is projected from the branch, a reaction of equal and opposite force to the force of the water jet takes place. This causes the branch to recoil in a direction opposite to the flow.