Air Locks in Plumbing

TROUBLE AT A KITCHEN MIXER TAP

Kitchen sink tap

If the air lock is ill the pipe supplying the hot water to a kitchen sink mixer you will need just a short length of garden hose. Connect one end of the hose to the outlet of the mixer.

Then squeeze the free end with your fingers or a hose clip to prevent water escaping, and turn on both the hot and the cold water. The cold water under mains pressure will flow up the hot-water outlet and force out the air lock.

FINDING THE CAUSE OF AIR LOCKS

Air locks occur when the water level in the cold-water storage tank (which is usually in the loft) falls more quickly than it can be replaced through the ball-valve inlet from the rising main. Eventually the tank empties and air enters the pipes. If air locks occur often, investigate three possible causes:

• The cold-water storage tank is too small.

• The pipe to the hot-water cylinder from the cold-water tank is too narrow.

• The ball valve in the tank is giving too weak a flow.

You will probably need to call in a plumber to deal with the first two, but see Ball valves for the third.

An air lock in a tap

When the flow of water from a tap - usually a hot-water tap - slows to a trickle or stops altogether, the most probable cause is an air bubble, or 'air lock' in the pipe.

YOU WILL NEED Length of 13 mm (fin) garden hose, hose connectors to fit your taps.

Connect one end of the hose to the tap that is giving you trouble, and the other end to the cold-water tap over the kitchen sink. The kitchen cold-water tap is supplied direct from the water main.

First, turn on the tap giving trouble and then the sink cold-water tap. The mains pressure will force the air bubble out of the system.

Refilling a hot-water system 'upwards'

Air locks are likely to occur when a hot-water system is refilled after it has been emptied.

To prevent this happening, fill the system 'upwards' by connecting one end of a hose to the cold tap over the sink and the other end to the lowest drain cock in the system. Open the drain cock and then turn on the cold tap slowly. Water will flow into the hot-water system, driving trapped air in front of it as it rises. If the pressure of the water should force the hose off the drain cock, fix it on again with a hose dip.

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