In today’s age, building’s external design is given more significance over its services design.Hence, there is a constant demand for innovative products which can work in complex and stringent architectural designs. There are many such innovative products available in the international markets which helps us in different ways in different challenging situations.
In particular, today we are discussing about AAV.
What is AAV ? And how does it function ?
- AAV stands for Air Admittance Valve.
- AAV is new innovative product which is basically a modified version of a regular PVC Vent cowl.
- AAV is a small device which has a diaphragm installed within and it keeps itself closed all the times and it can only open itself when it senses that there is a negative pressure created in the pipe line. These are basically the disturbances created in the pipes due to the heavy movements of air and liquids passing through. (ie. Pressure in pipe line is less than the atmospheric pressure)
- AAV keeps the entire Drainage and Vent lines sealed from the top and helps in keeping away the unwanted foul smell, harmful gases and bacteria away from entering in to the ducts and from the terrace roof.
- This device makes sure that the pipe lines do not sent the odour / air out side to the environment. It can only suck the air from outside.
- AAV also helps to reduce siphonage and noise to a significant level.
AAV’s mechanism works very well and it is commonly used in various types of building structures around the world.
However, today we shall see how the use of AAV may give arise to different big problems which can be really terrifying and even life threatening.
Let’s assume that there is a multi occupancy building structure, of which the top floor and roof top is owned by a single commercial owner, whois facing a lot of discomfort due to bad odour coming out from the soil and vent lines. So the owner decides to take an expert opinion on the matter. The plumbing consultant provides a simple solution to the owner that to remove the existing PVC Vent Cowls from the stacks and upgrade them with air admittance valves. Right after the old cowls were upgraded with the new ones; the problem of the bad smell was resolved and the owner was happy and satisfied even since.
In the same building, an occupant residing at a mid floor moves out of this flat and he is away for a very long time. Since there is no user in this flat, the water seal in the plumbing fixtures starts depleting due to heat and evaporation over time.Soon after the water seal level falls down the minimum level the seal brakes open &the foul smell, harmful gases and highly flammable methane gas starts entering into the occupants entire flat premises. The air pressure starts to neutralise itself through a broken water seal of a plumbing fixture and the diaphragm of the air admittance valve keeps itself closed and AAV acts as an end cap
Note: According to the principle, any pressure (positive or negative) finds the best possible way to neutralise itself, in most easiest& nearest way.
This scenario would be very lethal, since the highly flammable methane gas developed from the soil lines is entering only in the said closed flat and depositing it self in high quantum. Which indeed turns the entire flat as a potential bomb awaiting to be exploded and the none of the occupants (flats owner’s) neighbours are aware about the bomb which is ticking just the next door. It even makes more difficult because it does not give any sign or warning signals in advance.
AAVs can be a great solution for venting problems, but should never be the first choice. In fact, they should be the absolute last possible choice.
P.S. Venting of all the plumbing fixtures is a serious matter which is always taken very lightly and sometimes even ignored.
Caution! In any building structure, there must be at least one vent open to the atmosphere outside. An external, passive vent relieves positive pressure in the lines. No building should exclusively use AAVs – significant problems will result.
Sourabh A. Sheth
Sheetal Environs India Pvt. Ltd.
Licensed Plumbing Engineers, Consultants & Contractors
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