Air admittance valve vs. venting

[Jenkins]

I am installing an a stand alone island and need to reroute the ventilation for sink and dishwasher. I can either
A. Put in an air admittance valve under the sink

B. Run the ventilation under the slab and up through another wall about 9’ away

thoughts on the best option?

 

[Diehard]

IF allowed by your areas plumbing code, I would keep it simple and add a AAV.

 

[frodo]

I disagree, AAv's fail. a vent out the roof will not fail

 

[wood4d]

frodo hates aavs. I use them for island sinks exclusively because they are an easy fix verses elaborate plumbing.

 

[frodo]

frodo hates aavs. I use them for island sinks exclusively because they are an easy fix verses elaborate plumbing.

lol



Why YES, Yes I do hate AAV's and refuse to install them
here is why.

they are usually installed wrong
when the sewer backs up,sewage comes out the aav
they leak over time and funk up a house
and lets be truthful. they are used because someone is to lazy to run a vent

now lets talk about how it works.
it lets air into the system when it feels a change in pressure
WELL...to let in pressure means the diaphragm opens [ open means air can flow in both directions]
letting in air as well as letting out funky air

 

[Diehard]

AAV's may not be an ideal installation but they work when used properly.
They are not meant to be installed wrong.

 

[Jenkins]

I appreciate all of your opinions, this is some great insight. Now I just have to make a decision.

 

[Jenkins]

I disagree, AAv's fail. a vent out the roof will not fail

View attachment 23729

So from the drawing, is that an 1-1/2 pipe or fall for the vent pipe? ( I am assuming pipe since 1-1/2 fall seems extreme)

 

[Diehard]

Yes you assumed correctly.
But as you may already know,vents are required to slope back to the drains.

 

[frodo]

So from the drawing, is that an 1-1/2 pipe or fall for the vent pipe? ( I am assuming pipe since 1-1/2 fall seems extreme)

When roughing in the drain for the kitchen sink. the drain needs to be 8'' off center of the sink.
and.. which ever side you plumb the drain. the garbage disposal will hang on the opposite side

typically. you want the garbage disposal on the side nearest the dishwasher

 

[Jenkins]

@frodo, I guess my question is. If I go the route of venting it the way you describe, does the 1-1/2” vent line need to have any sort of fall to it?

Also, your answer was helpful also, those numbers really helped

 

[frodo]

yes. the vent should fall from the wall back to the island
rain water, condensation, can drip back to the drain line

1/4'' per foot

 

[Mitchell-DIY-Guy]

My own opinion is an AAV vs. busting up a slab? No brainer. Use an AAV.
So, AAV's "fail"? Oh, my. Bring a $5 bill to a home center and walk home with a new one, in the case that they do fail.

The "Carson Dunlap" diagram in reply #5 isn't quite right. It says, "System at rest: sealing mechanism is closed when there is positive pressure from gases"...Well, the sealing mechanism is held closed by a spring, REGARDLESS of the gases. It's nothing but a check valve for air, and it flows in one direction (INTO the piping system). Because it is held sealed by a spring there is a "cracking pressure" that is required to open it; the cracking pressure is the pressure differential between the input side and the output side.

Because it is meant for air, not solid waste, sure if there is backpressure from sewage it may very well spill out. If that's the case it may be installed wrong; there are right ways and wrong ways to install them.

Now, if you can adequately install a hard vent pipe, without busting slabs, opening walls, or other highly invasive means or if it is required absolutely, then do it.

 

[wood4d]

just to be accurate...there is no spring. Thats how the $5 cheater vents worked. The aavs are 20 ish and operate on pressure. Im old and hate them too but need to make $ so I use them on islands.

 

[Mitchell-DIY-Guy]

The ones that I had purchased were Oatey 39012. Cost about $5 when I bought them. Supply House has them for less than $3. Spring loaded, rubber diaphragm. I never used them in place of venting, but in islands, or in remote sinks..."just in case" the system screams for more air. Not sure they ever even opened, but in case--they are there.

I suppose there are all kinds at all price points.

 

[Diehard]

The slab busting is also required for the drain.

 

[voletl]

The slab busting is also required for the drain.

I know right I guess he thought that the drain line was going to go somewhere else

 

[Jenkins]

Just an FYI I ended up cutting the slab to run electrical and water for the ice maker. The question was really to make an informed decision because I have seen pros and cons for each. I appreciate all of your thoughts and views.

 

[frodo]

insulate that ice maker line
it will keep the rocks from rubbing a hole in it over time

 

[Jenkins]

insulate that ice maker line
it will keep the rocks from rubbing a hole in it over time

I am going to run it through pvc. To avoid future problems