Inspected a newer house, all of the 1st floor sinks use an AAV for venting, and all seem to be installed very short to me. I understand the concept and use of an AAV, but I think this should be installed higher to achieve proper venting. I ran a lot of water, and with a full sink, it did gurgle and drain a little slow…
Andy, I don’t have it handy, but the install guides spec out the height of the device and other pertinent details for these AAV’s.
I think it’s 4 inch above horizontal branch.
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Just saw one that said 200mm, which equals about 7"… Regardless, this one’s too short, and affects drainage.
What effect on the drainage did you observe?
The height wouldnt affect drainage. The height is to prevent water from entering the device. Either the p-trap was clogged, or the flapper on the vent is going bad, and not letting air in. However, when they go bad, its usually the other way around. (letting air out)
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If you think it’s too short then by all means write it up, it also appears to be hard riding a shut-off valve for the sink fixture.
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It was fine until I filled the sink and then opened it, drained slowly and gurgled a lot. This is the kitchen drain, but all bathroom drains were installed like this. I didn’t get any issues with the bathroom drains, but the kitchen sink, being much bigger, of course had a bigger load when I opened the drain.
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This is an 8BR/5 bath vacation rental home near Disney - likely won’t have anything done. I’m writing it up so that if something is noticed - “Why won’t the kitchen sink drain?” - it’ll explain it.
I concur with, Dom… Oatey AAV installation guide reads, minimum of 4” above the horizontal branch drain, 6” above any insulation material and within 15 degrees of vertical .
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I concur. By looking at the AAV setup, it is clearly short
It might be working perfectly. Restricted air flow is one of the known limitations of using an AAV - it only lets in so much air:
- Performance Issues: AAVs may not function as effectively as traditional vent pipes. In some cases, the valve may fail to open properly, leading to drainage issues or the accumulation of sewer gases. AAVs also have limitations on the volume of air they can admit into the plumbing system. In a busy kitchen or bathroom with multiple fixtures draining simultaneously there may be insufficient airflow, leading to slow drainage or gurgling sounds.
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Thing about AAVs:
they have a rubber seal that needs replacement every so often.
Or replace the whole thing.
Bet Mr. Homebuyer did not know that.
I always thought that they had to be installed above the flood level rim.
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On topic, though not necessarily your region:
7.5.9.2. Air Admittance Valves
(1) Air admittance valves shall only be used to vent,
(a) fixtures in buildings undergoing renovation, and
(b) installations where connection to a vent may not be practical.
(2) The air admittance valves shall be located,
(a) above the flood level rim of the fixture it serves,
(b) within the maximum developed length permitted for the vent ,
(c) not less than 150 mm above insulation materials, and
(d) installed in a location not subject to back pressure.
(3) Air admittance valves shall,
(a) only vent fixtures located on the same storey , and
(b) be connected to the horizontal fixture drain .
7.5.9.3. Installation Conditions
(1) Air admittance valves shall not be installed in supply or return air plenums , or in locations where they may be exposed to freezing temperatures.
(2) Air admittance valves shall be installed in accordance with the manufacturer’s installation instructions.
(3) Air admittance valves shall be rated for the size of vent pipe to which they are connected.
(4) Installed air admittance valves shall be,
(a) accessible , and
(b) located in a space that allows air to enter the valve.
(5) Every drainage system shall have one vent that terminates to open air in conformance with Sentence 7.5.6.2.(1).
Sadly that does not include the condition I would want:
1) AAV’s must have a durable clearly readable label stating an install date and expiration date for the rubber seal, after which the seal or AAV should be replaced.
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I must confess - I didn’t know that.
