Air admittance valves

[TomR]

In another thread (about ABS pipe), Nestork wrote:

..., you may be able to use an air admittance valve here....,

Loading Image...



An air admittance valve has to be down stream of, and at least 4 inches
above the p-trap, but check your local plumbing code. Your local code
may be different.


++++++++



I have a situation where I may want to use an air admittance valve and I
have a couple of questions about where to place it etc.



In the photo link above, the air admittance valve is below the level of the
sink.



If there is ever a blockage somewhere downstream in the sink drain line,
the sink would fill up with water (of course). But, would that mean that
water would back up and overflow out of the air admittance valve?



Also, if the sink clogs, and I use a plunger to try to plunge out the drain
line, would water back up out of the air admittance valve? I know that I
would need to seal up the overflow hole in the sink while plunging, but how
would I be able to seal up the air admittance valve to keep water from
coming out?



The sink that I have has a significant slow drainage problem. I have snaked
out the drain for at least 15-feet and I don't think the slow drainage is
due to a clogged drain line. (I still need to do more work to completely
verify that). I suspect that the slow drainage is due to the fact that the
sink is too far from a vertical vent stack. So, I am thinking of installing
an air admittance valve.



My sink setup looks similar to the photo -- a sink with a P-trap that then
drops down inside the wall. It's a bathroom with tile on the bathroom side
of the wall under the sink. But, the other side of the wall is in a closet
and I can open that side of the wall up to install the air admittance valve.
Or, if the air admittance valve can be tied into the horizontal part of the
P-trap, maybe I could just put it under the sink and not hidden in a wall if
that is an option.

[t***@optonline.net]

Post by TomR
..., you may be able to use an air admittance valve here....,
http://plumbinghow1.files.wordpress.com/2013/02/air-admittance-valve-install2.jpg
An air admittance valve has to be down stream of, and at least 4 inches
above the p-trap, but check your local plumbing code. Your local code
may be different.
++++++++
I have a situation where I may want to use an air admittance valve and I
have a couple of questions about where to place it etc.
In the photo link above, the air admittance valve is below the level of the
sink.
If there is ever a blockage somewhere downstream in the sink drain line,
the sink would fill up with water (of course). But, would that mean that
water would back up and overflow out of the air admittance valve?

It's an air admittance valve, not a water out valve, ie it's like
a check valve that only allows flow in one direction, that being
air in. If it malfunctioned for some reason and got stuck, then
water could flow out.

[TomR]

Post by t***@optonline.net

Post by TomR
In the photo link above, the air admittance valve is below the level of the
sink.
If there is ever a blockage somewhere downstream in the sink drain line,
the sink would fill up with water (of course). But, would that mean that
water would back up and overflow out of the air admittance valve?

It's an air admittance valve, not a water out valve, ie it's like
a check valve that only allows flow in one direction, that being
air in. If it malfunctioned for some reason and got stuck, then
water could flow out.

That makes sense. I guess I was thinking that while the AAV can draw air
in, maybe the seal is not watertight so if it was full of water it might
leak inside the wall. But, I think you're probably right and it may not be
an issue.

[c***@snyder.on.ca]

Post by TomR

Post by t***@optonline.net

Post by TomR
In the photo link above, the air admittance valve is below the level of the
sink.
If there is ever a blockage somewhere downstream in the sink drain line,
the sink would fill up with water (of course). But, would that mean that
water would back up and overflow out of the air admittance valve?

It's an air admittance valve, not a water out valve, ie it's like
a check valve that only allows flow in one direction, that being
air in. If it malfunctioned for some reason and got stuck, then
water could flow out.

That makes sense. I guess I was thinking that while the AAV can draw air
in, maybe the seal is not watertight so if it was full of water it might
leak inside the wall. But, I think you're probably right and it may not be
an issue.

Water should never get to the AAV- is should have a pipe full of air
between it and the water.

[c***@snyder.on.ca]

Post by TomR
..., you may be able to use an air admittance valve here....,
http://plumbinghow1.files.wordpress.com/2013/02/air-admittance-valve-install2.jpg
An air admittance valve has to be down stream of, and at least 4 inches
above the p-trap, but check your local plumbing code. Your local code
may be different.
++++++++
I have a situation where I may want to use an air admittance valve and I
have a couple of questions about where to place it etc.
In the photo link above, the air admittance valve is below the level of the
sink.
If there is ever a blockage somewhere downstream in the sink drain line,
the sink would fill up with water (of course). But, would that mean that
water would back up and overflow out of the air admittance valve?

If the valve malfunctions, yes - which is why it should be 4 inches
above the maximum water level in the sink.

Post by TomR
Also, if the sink clogs, and I use a plunger to try to plunge out the drain
line, would water back up out of the air admittance valve? I know that I
would need to seal up the overflow hole in the sink while plunging, but how
would I be able to seal up the air admittance valve to keep water from
coming out?

It is a one way valve. If it is functioning properly it will let air
in, but not out - they are referred to around here as "automatic
vents" They cannot be allowed to vent gasses OUT of the drain - only
allow air in.

Post by TomR
The sink that I have has a significant slow drainage problem. I have snaked
out the drain for at least 15-feet and I don't think the slow drainage is
due to a clogged drain line. (I still need to do more work to completely
verify that). I suspect that the slow drainage is due to the fact that the
sink is too far from a vertical vent stack. So, I am thinking of installing
an air admittance valve.
My sink setup looks similar to the photo -- a sink with a P-trap that then
drops down inside the wall. It's a bathroom with tile on the bathroom side
of the wall under the sink. But, the other side of the wall is in a closet
and I can open that side of the wall up to install the air admittance valve.
Or, if the air admittance valve can be tied into the horizontal part of the
P-trap, maybe I could just put it under the sink and not hidden in a wall if
that is an option.

It is an option if you can get it between the trap and the wall - not
the preferred location (which is above the overflow level) - but being
accessible may outweigh the hieght issue.

[nestork]

;3088932']
I have a situation where I may want to use an air admittance valve and
have a couple of questions about where to place it etc.
In the photo link above, the air admittance valve is below the level o
the
sink. If there is ever a blockage somewhere downstream in the sin
drain line, the sink would fill up with water (of course). But, woul
that mean that
water would back up and overflow out of the air admittance valve?

No, it wouldn't. Lemme explain why you need venting, and then you'l
understand why you can use an air admittance valve instead of a ven
pipe.

If you've ever been in a subway station when the train leaves, you'l
feel a strong wind. That wind is caused by air being sucked into th
tunnel behind the train. An identical sort of thing happens when wate
drains down a drain pipe, and the resulting partial vaccuum tha
develops behind the draining water can be strong enough to suck th
water out of your p-trap. You don't want that to happen because tha
water forms a physical barrier between the putrid air in the city'
sewer system and the air in your home that you breathe. An ai
admittance valve (also commonly called a "Stoddard Valve", after th
company that first marketed them for this purpose) is nothing more tha
a spring loaded check valve. Whenever the partial vaccuum behind th
draining water becomes strong enough that it threatens to suck the wate
out of the p-trap, the Air Admittance Valve opens, allowing air into th
drain pipe behind the draining water, thereby ensuring that the water i
the p-trap won't gets sucked out.

But, because it's a CHECK valve, it only opens when there's a partia
vaccuum in the drain line, not when there's a positive pressure in th
drain pipe, which is what you'd have if your water was backing up in th
drain pipe. That is, it allows air INTO the drain pipe, but doesn'
allow anything to come OUT OF the drain pipe.

Also, if the sink clogs, and I use a plunger to try to plunge out th
drain
line, would water back up out of the air admittance valve? I know tha
I
would need to seal up the overflow hole in the sink while plunging, bu
how
would I be able to seal up the air admittance valve to keep water from
coming out?

If you plunger that drain like a rabid gorilla, you could possibl
create enough suction to cause the AAV to open and allow some air in
but any pressure inside the drain pipe will close the AAV.

The sink that I have has a significant slow drainage problem. I hav
snaked
out the drain for at least 15-feet and I don't think the slow drainag
is
due to a clogged drain line. (I still need to do more work to completel
verify that). I suspect that the slow drainage is due to the fact tha
the
sink is too far from a vertical vent stack. So, I am thinking o
installing
an air admittance valve.

If this is a bathroom sink, then I may be able to save you some time an
money. Often bathroom sinks drain slowly because the overflow drai
gets all clogged up with hair, soap scum, dead skin, and all that kind
stuff.

So, what happens is that when you pull the plug on that sink, air get
trapped under the clog in the overflow channel. As the water level i
the sink drops, the hydrostatic pressure on that trapped air goes dow
and the trapped air expands, pinching off the flow of water down th
drain. That's what causes the slow drainage; the expanding air bubbl
under the clog in the overflow drain is pinching off the flow of wate
down the drain. If your drain initially flows normally (for the firs
few seconds, and then gradually slows down to a crawl, and then you se
a bubble come up out of the drain, or even if you don't and the drai
suddenly flows quickly again, that's typical of a clogged overflo
channel.

What you need to do is glue a 1 1/4 inch Hub Trap Adapter fitting to a
1/4 inch clean out fitting, like this:

[image
Loading Image...]

Cement the above (which will tighten around your sink drain's tail
piece) to a 1 1/4 or 1 1/2 inch clean out:

[image:
Loading Image...]

Not the clean out has a threaded plastic cap which allows you to drain
the water without removing the trap adapter from the sink tail piece.

You can tighten that onto your sink's tail piece and screw the clean
out plug into the bottom so that no water comes out the bottom of your
contraption. Set a 5 gallon pail under the sink drain, put a board
across the top of the pail and rest your contraption on the board so
that it's supported from below. Now, fill your sink full of water until
the overflow spout gets filled as well. Now plunger that sink. Since
the water can't flow out the sink drain cuz of your contraption blocking
everything at that end, the water surge from the plunger goes up the
overflow channel and clears all the crap out of there. You'll be
surprised how much crap will accumulate in that overflow channel. Once
you have a whole bunch of crap in your sink that all came out of the
overflow channel, take the board away, and unscrew the plug on the clean
out fitting so that the water in the sink (and all the crap in it)
drains into your pail. Flush all that stuff down your toilet or throw
it in your back yard. When you put your sink drain back together again
(provided it doesn't leak) it'll drain just like it did when it was
new.

I find that I regularily have to clean out the overflow channels on my
bathroom sinks, especially when I have female tenants living in the
apartment because of their long hair.

My sink setup looks similar to the photo -- a sink with a P-trap that then
drops down inside the wall. It's a bathroom with tile on the bathroom side
of the wall under the sink. But, the other side of the wall is in a closet
and I can open that side of the wall up to install the air admittance valve.
Or, if the air admittance valve can be tied into the horizontal part of the
P-trap, maybe I could just put it under the sink and not hidden in a wall if
that is an option.

Watch the way the sink drains. If it slows to a crawl, and then you see
a bubble and it speeds up again, it's a clogged overflow drain, not the
lack of an AAV. An AAV won't help a sink drain; it'll just prevent the
water in the p-trap from getting sucked out. But, the sink won't drain
any better. Clearing a clogged bathroom sink overflow drain will
definitely make the sink drain better because of what happens when air
is trapped in the drain as described above.

[TomR]

;3088932']
I have a situation where I may want to use an air admittance valve and I
have a couple of questions about where to place it etc.

If this is a bathroom sink, then I may be able to save you some time and
money. Often bathroom sinks drain slowly because the overflow drain
gets all clogged up with hair, soap scum, dead skin, and all that kinda
stuff.
What you need to do is glue a 1 1/4 inch Hub Trap Adapter fitting to a 1
http://www.carterlumber.com/Image/xeEvnSiB8E6eXkNns9X56A/250/350/6319123.JPG]
Cement the above (which will tighten around your sink drain's tail
http://static.hardwarestore.com/media/product/296079_front200.jpg]
Now the clean out has a threaded plastic cap which allows you to drain
the water without removing the trap adapter from the sink tail piece. . .
. ,

Interesting idea.

[nestork]

;3089742']Interesting idea.

Do that before you start adding an air admittance valve.

If you're uncomfortable with the idea of taking your bathroom sink'
P-trap apart, cuz of fear it might leak when you go to put it bac
together, clear your drain another way:

Go to your local auto wrecker and liberate a car speedometer cable for
$1. Take the cable core out of it, cut to length, flaring the wires o
the end a bit to scrape the inside of the over flow channel, put that i
a cordless drill, and use it as a poor man's motorized snake to clea
your clogged up over flow channel.

Snake with the sink full so that even the overflow channel is submerge
if you can get to that point. Once you clear the blockage, run water i
the sink to keep water flowing down the overflow channel while you
stick a bent wire into the openings in your drain where the water fro
the overflow channel flows into


--
nestork