Screw on Fixing: With the screw-type fixing, the coupling supplied with the AAV will have a thread within it and on the base of the AAV itself will be a thread. Simply fit the coupling to the top of the vertical pipe and then screw the valve down into the coupling until it is tight

You can use compression fittings if you wish but they tend to be big and bulky. See our project here on UPVC compression fittings for more help. By installing them inside they are fully protected from the elements and should hopefully go on for many years.As good and useful as air admittance valves can be they can also cause some problems, especially when they become old and worn. Rubber Finger/Push-fit: The bottom of the valve features fairly stiff rubber banded bellow-like belt. The “fingers” of the belt are pushed down into the top of the pipe and grip the inside holding it in place. To ease fitting some washing up liquid is often used to help it slip down into place. As it can be easily pulled out, if there are any issues it can easily be removed for repair or replaced. All pipework contains air and in it’s natural state it sits in the pipes at the same atmospheric or neutral pressure that any other undisturbed air sits at.

In the majority of cases and in most homes in the UK, the balance of pressure within a waste pipe system is maintained through a soil vent system. This is just a vertical extension of the soil pipe system that stops beyond the highest drainage point in the property. In almost all instances they are installed internally. Only those made especially for use outside can be used externally as they need to be weather and frost proof to prevent them freezing up and stopping working, in which case the above issues can occur. Solvent Weld: The base of the unit features a collar that slips over the top of a 110mm pipe and is then glued in position using solvent weld adhesive. This will ensure a firm fitting but if the unit fails the only option for removal is to cut the top of the pipe off Pipe Size Compatibility: Ensure the valve is compatible with the size of your waste pipe. Universal valves are versatile, while specific size valves provide a tailored fit. However, like the 110mm versions, the smaller ones must also finish above the highest flood level of the room the valve is in e.g. in the case of the basin above, it must be higher than the overflow of that basin.

Installing 110mm Air Admittance Valves

Once you have found the ideal install location the next task is to cut the existing waste pipe so that you can fit a T-piece or equal-T as it’s known to run the vertical pipe to fit your AAV.