When you flush waste water from a toilet, bath or sink the water will flow along the waste pipe and air is carried along with it. As the water and air flow down the pipe it will cause a change in pressure in the pipework and air will be drawn into the system. Have you ever heard the gurgling sounds coming from the plughole or drain when you’re emptying the sink for example? Often this will be from plugholes, but air will enter the system anywhere it can in order to reduce the negative pressure. This is what you’re hearing, air being drawn into the pipework system in order to stop a vacuum. If there is an issue with pressure in the pipework system and not enough air is able to be drawn in, it can cause problems such as waste water coming back up from the traps. If you’ve ever smelt that “drain smell” coming from a plughole then this is likely what is happening.
Usually, the way this problem is tackled is by venting the system at roof level using a soil vent pipe. This allows air in (and out) of the pipe at a level where any gasses that are expelled will be expelled out of reach of neighbours noses! This method will allow the air to be drawn in at this point also, and as air or water will always use the path of least resistance then it will stop the gurgling noises and the foul smells coming from your plugholes as the pressure in the pipe system will be normalised and air will not need to be drawn in from these points and waste water will not return out of the traps. Sometimes a pipe vent above roof level is not always possible, this is where you might use an air admittance valve.
DURGO AIR ADMITTANCE VALVE PROBLEMS INSTALL
How high should you install the air admittance valve? The short answer is a minimum of 200mm above any water entry point.Īs a general rule, a soil pipe vent should never be vented less than 3m from a window otherwise you or your neighbours will be gassed out by foul odours coming from the vent! Air admittance valve installation height Reasons why you may not be able to use a vent above roof level is that there may be a neighbour with a loft conversion, or surrounding taller buildings, or when the building has roof windows.
So if you imagine your soil pipe run, then durgo valve / AAV must be fitted above the highest connection to the soil pipe from any sink, bath or toilet that is connected to it. Usually you’ll find the installed at the very end of the soil pipe. If you need to, you can install them in line using a soil pipe junction. You’d usually install the air admittance valve within the loft or it is boxed in within the property. Sometimes they’ll be installed in airing cupboards, usually to keep them out of sight.
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