AUTO AIR VENTS

These are often used in a high point (of course), and most often found in the airing cupboard.

They are fitted to just about all the combi boilers and are subject to leaking or sticking.

They work like a ball cock in reverse. Instead of letting in water like a water valve that you would find in the toilet, they let air out when the float drops. The snag is that very often a piece of rubbish gets caught underneath the turn off point and the thing leaks.

The best option is to drain down the system and replace the vent.

Some auto air vents have a shut off valve built in. These are supposed to shut the water off when the valve is removed. It is a bit risky to rely on this. When replacing the valve it is a good idea to put a turn off valve on the pipe under it if you have room so that if it goes wrong again it is easy to change. You can’t do this on a combi of course.

These vents are quite standard except they come in two sizes, and with some combi's you have to get the right one for the model.  If you can, take the old one into your supplier and see if he can match it up.