The Air Admittance Valve

An air admittance valve can be compared in its operation to a rather large non-return type of valve, where the air is allowed to enter into your system through the valve but does not allow foul smelling air escape into the atmosphere around your WC.

These types of valves are made and fitted to lower the number of ventilation pipes for a building, that would usually have its vent routed out through the roof and away into the atmosphere. When they are fitted, they are normally in the closed position and are there to stop foul air from escaping from the pipework system in a normal atmospheric condition or if positive pressure is created in a soil stack or waste pipe, from the discharge from appliances or changes in pressure in a drain system. A South West London Plumber is familiar with this system.
If a negative pressure is experienced, the valve will automatically open and let air enter the stack, this has the affect of equalising the pressures and therefore stops the loss of water seals inside the traps for appliances. Air admittance valves can be found in a varied range of sizes and sometimes the main waste drainage stack can be fitted with the air admittance valve. These valves are generally used when two soil stacks exist in the same building, or where there are a number of buildings that close to each other, the valve makes it unnecessary to route the highest point of the soil discharge stack out through the roof. The air admittance valve is best to be installed above the critical level for any spillages of an appliance.
The air admittance valve can be fitted by South West London Plumbers. If the valve is not fitted in that location and a blockage occurs it would back up and cause the valve to lose its water tight integrity. As long as the valve is well insulated it can be fitted in exposed locations like loft spaces, as condensation in the pipework can freeze.