Air Admittance Valves, sometimes called Durgo Valves, are one-way air valves that can be installed instead of Soil Vent Pipes, or sometimes in addition to them, to help keep the pressure in soil and waste systems balanced.
An air admittance valve (AAV) is an alternative option to fitting a vent in a soil pipe – a soil pipe vent if you will. It opens automatically when water enters the soil pipe and closes when the water has passed into the drain.
Foul Odours and Health Concerns
If a soil vent pipe becomes blocked or damaged, foul odours from trapped gases can infiltrate living spaces.
I have had plumbers tell us that sewer flies and bugs have been seen at failed air admittance valves. So if you detect a sewer odor under and around your sink or in the attic, the AAV could have let you down.
The soil vent pipe is essential for ensuring your home has clean, safe air. Unfortunately, we've come across homes where this was damaged, installed incorrectly, or not installed at all! Yet if it isn't working correctly, your home is at risk of being exposed to foul-smelling, potentially dangerous gasses.
Without the vent pipe, the liquid will attempt to draw air through the P-traps on your tub or sink. This will create a gurgling sound.
Air Admittance Valves (AAV) — Oatey ®Sure-Vents® — are mechanical devices installed to a plumbing fixture, replacing a secondary vent. These valves allow one-way ventilation, removing the need to connect to an existing venting system or run a separate, potentially unsightly ventilation system.
Potential issues with air admittance valves
Sometimes unwanted smells may be emitted, gargling sounds may occur or wastewater comes up from the soil pipes into the sink. All of which are signs that there may be an issue with the air admittance valve. Occasionally the valve may get stuck.
The Studor vent lets that air to be sucked in the pipe during water flow but doesn't let sewer gas escape out. Code is the thing that determines pipe size and also water flow. Hence no studor vents are permitted to toilets because more air is required to keep water flow going with more waste added to the toilet.
The document states that the opening of ventilation pipes should be located at least 900mm above any building within three metres of the pipe. The vent will also need to be protected with a wire cage or perforated to prevent debris or birds from entering it.
If you have downward-sloped pipes, your toilet will most likely work without a vent. Gravity does a lot of the heavy lifting anyway. However, using the toilet without a vent means you don't have any protection against gases traveling up your drain pipes and into your home.
Your soil stacks and drain stacks funnel wastewater, including human waste, soap scum and food particles to the municipal sewer system. The vent stacks funnel sewer gases to the outside and allow fresh air into the plumbing system.
Automatic air vents are spring type devices often referred to as in-line or cheater vents, while air admittance valves have no spring. Air admittance valves are more expensive and are approved in many jurisdictions where in-line and cheater vents are not because of their moving parts (springs).
The short answer is a minimum of 200mm above any water entry point. 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.
Put simply, soil pipes are designed to carry soiled water (blackwater) from toilets, urinals, or bidets, and waste pipes are designed to carry wastewater (greywater) from sinks, showers, baths and washing machines down into the mains sewer (or a storage/treatment plant if you have an off-mains system).
Air admittance valves are not permitted in spaces where pressure conditions adversely affect the valve's operation. They are also not allowed in concealed wall and ceiling spaces used as plenums as part of an air distribution system that is under negative or positive pressure.
A "Crown Vent" is a vent that is located within 2 pipe diameters of the trap it is serving. The issue is if the vent is that close it is more likely to be subjected to fouling of hair, soap oils, grease, and other debris.
An Air Admittance Valve (AAV), which you may also hear referred to as a Studor Vent, Studor AAV or Mini Vent, is a one-way mechanical valve that is installed locally at the site of a plumbing fixture, allowing proper venting to occur without a connection to a larger venting system and stack vent.
Air Admittance Valve - an alternative to installing a vent pipe that allows the soil stack to terminate inside the property.
Air Admittance Valves, sometimes called Durgo Valves, are one-way air valves that can be installed instead of Soil Vent Pipes, or sometimes in addition to them, to help keep the pressure in soil and waste systems balanced.
Durgo valves activate when wastewater is sent into the waste pipe, causing negative pressure. The valve opens to allow air in, equalising the pressure. Once balance is achieved, the valve closes, preventing odours from escaping into your home.
Air admittance valves have a typical life expectancy of 20-30 years, so if you start to have issues with sewer gases or smells being released around your sink or in the attic-wherever installed- the air admittance valve could be faulty or failed and should be replaced as soon as possible.
Air admittance valves are typically placed between the P-trap of a fixture and the drain line. They're usually mounted on one leg of a sanitary tee, with the other leg going to the drain. The unit must be placed per local codes and the manufacturer's instructions.
It must be located a minimum of 4” above the horizontal branch drain, 6” above any insulation material and within 15 degrees of vertical.