auto vent use

[billyoung]

We built a room addition in a rural area and added a toilet and sink. OK. We were told we could use an auto vent at the sink and that it would vent the toilet too, which is right beside it. I will describe the drain: there is a 3" going straight down from the toilet about a foot or so and then a 45, then another 1' and the 11/2" from the sink Ys into the 3", then it goes 2' still at the 45 angle and then 45s into a horizontal pipe for 4' and then 45s with a cleanout to the outside where it runs horizontal for 4' turns 45 and drops at a 45 angle down about 5' to Y into the line coming out of the basement, then 4' to the septic. That's the initial layout. The sink has a properly installed auto vent. It seemed to work fine for a while and then the toilet wouldn't flush the water out. It would back up. I checked the clean-out and there was no water there, so I figured I had some kind of air lock preventing the water from going down. So, I installed a 11/2" y into the 3" above the intersection of the sink y into the 3" and then popped a 11/2" through the bathroom floor and above the toilet tank and installed another auto vent. We were hoping to not go through to the outside. Thought we had a good understanding about the use of the auto vent at the sink, later found out that each branch needed an auto vent, so installed the second one for the toilet. There has still been some air locks from time to time - some time it works. We want to resolve it once and for all. Where would you go from here? thanks for your time, Perplexed.

 

[Dlarrivee]

Air locks?

 

[Sponsor]

 

[billyoung]

yeah, the water just doesn't go down even though there is nothing visible stopping it. I assume it is some sort of vacuum pressure situation that is created. Like I said, I removed the clean out plug thinking I would see something plugging things up, but there was nothing, not even water. If I flushed too many times, the water would come back up the top of the toilet and out. That is why I am asking about this. I have not had experience with the auto vents and question whether they are working or not or should be working, or am I using them in the wrong way. Thanks for asking. I don't know what else to say. The only thing i know to do is retrofit a vent from the sink to the toilet to the roof - a lot of work if something just needs to be tweeked.

 

[Tom Sawyer]

There is no such thing as an "air lock" if you toilet is not flushing it's because there is either something clogging the drain line or there is a big sag in the pipe that acts as a secondary trap. Vents do not cause slow drains

 

[Jadnashua]

Or, there's a clog in the toilet itself...a comb, pen, pencil, tampon, etc. It can be sporatic depending on what's being flushed...all liquids, or paper, or solids depending on how they happen to move.

 

[billyoung]

Thanks, Tom, for replying. I admit it is a freakish thing. At one time I even used a power snake through the clean out just to make sure - clean as a whistle. So, I went backwards from the cleanout back up to the fixtures and the auto vents and couldn't find anything. I tested this 50 times with clear water. Does it sound like the auto vents are in the right place to function properly? I tried to describe where they were installed. There was a time when I would take the autovent off of the pipe by the toilet tank and the water would then run out immediately. If I put the av back in place it worked maybe maybe not, but then seemed at some time to stop things up again until I took it off. I've been scratching my head about this - believe me.

 

[billyoung]

Jadnashua, thanks for the reply. I have tested this many many times with clear water - there is some weird pressure thing going on - I have popped the autovent on and off, and mostly when it is off, it works, and when after some testing with it on it stops again, I pop it off and it runs right out. I tried to describe how I installed the av(s) does that sound like the right application. When I was building, another guy was doing this bathroom and heard from someone that the av would take care of both units, but I found out later, when the problems began popping up and he was gone, that each branch needs its own av, so that is when I put in the second one. I have been trying to get on top of this ever since and wonder if I need to change the venting scheme and get one to the roof. What do you think? do you have questions that I could answer to bring more clarity. Thanks for your time. Just had a thought - it acts like when you suck water up in a straw and then hold your finger on the end. I just don't know how to correct what is there so it flows.

 

[billyoung]

Tom, also, this isn't a slow drain - it goes nowhere. The toilet can be absolutely filled to the brim - I can then take off the clean out and there is no water either up or down from there and the water stays in the toilet. I can plunge it and it all just splashes out. I keep remembering different things that have happened - maybe will be the key to unlock this thing. Thanks.

 

[Jadnashua]

You likely have something in the trapway of the toilet or maybe you used a wax ring with a funnel, or a double one and the wax is partially blocking the outlet of the toilet.

You also can't have an AAV as the only vent on a line as sometimes, air needs to move both ways, and an AAV is a one-way valve.

 

[Jimbo]

Every plumbing fixture is self-venting. Any air needed to let the water flow just comes right in through the drain. problem is....that siphons the trap and odor becomes an issue...HENCE the need for vents. Slow drains are clogged, NOT vent problems.

 

[Tom Sawyer]

If taking the aav off makes the toilet flush then that tells me there is either an obstruction in the drain line or more likely a sag that is trapping water. Normally an AAV lets air into the system but if you have an obstruction or sag in the line then it is doing nothing because the water is being trapped between the obstruction and the fixture. Removing the AAV lets that air move out of the system and the water from the fixture in. Look for a big sagging spot in the toilet line. You may have to get someone in with a sewer camera.

 

[billyoung]

OK, thanks, Jim - I'm trying to figure out where to go from here. I've taken the toilet off and checked all of that and found it OK. When you say the next sentence, I get confused because it seems contrary to the directions to install the AV & I've always seen them used at the end of, mostly sinks, attached to and above the trap without any other direct vent. As another responder questioned, there are no sagging lines, it looks like a good plumbing job, all of the fittings and straight lines. Thanks, again, I do appreciate your response. I have actually worked on this thing from time to time for about a year, whenever it acts up again. The thing that is odd to me is how I can take off the cleanout and there is no water in the lines up or down and yet, the toilet won't release. argh! as Snoopy might say.

 

[Tom Sawyer]

That's because there's a big sag in the line...

 

[billyoung]

Tom, thanks again, but I don't see anything like that - the sag or obstruction - most of the horizontal lines I can see and they are all straight and good and looks like good plumbing - 3" PVC. Also, I can remove the septic lid and watch the water flow into it when the toilet releases or if the sink is running. Does it sound like to you, from my description of the drain and AV set up that that is as it should be, or at least nothing glaringly wrong? Believe me, I've looked at books, AV how-tos, talked to guys - you and others are giving things to think about and look for things with a fresh perspective. Tomorrow I'm trying again - I don't want to do anything drastic like running vent pipes to the outside if I don't have to - the thing is, this can work fine for a while and then go kablooey - it is a 3rd bathroom alternative in the home, but it seems like we should be able to get it working consistently without worrying if it will act up when a guest is using it. Thanks very much.

 

[billyoung]

Thanks, Jimbo, you are adding to my understanding about vents and traps, the only thing I think is different is that this is not a clogged drain or a slow drain - it just will not leave the toilet bowl - at least sometimes. It might work fine for a period, but then, without reasons I can determine, it backs up. That's why I said originally that it seems like an air lock - like holding water in a straw. Thanks for your time.

 

[hj]

quote; There is no such thing as an "air lock"

I hope you are not a plumber if you say that. Of course there are "air locks". That is one of the deficiencies of an AAV, because they CAN create an air lock. When the toilet does not flush, remove one of the AAVs and then try it. If it flushes and/or you feel air pushing OUT of the AAVs connection, then you DO have an air lock, and it is caused by "something" in the line creating a blockage preventing the air from being evacuated ahead of the water.

 

[billyoung]

hj, thank you for validating what I have been thinking with this thing; an air lock was the only way I could describe it - like a finger holding water in a straw, but I still don't know what the something could be. Did you read the initial post and the description of the layout? The thing that is new to me about the layout is that the toilet drains straight down 1' to a 45 and then 2' or so to another 45 to bring it to nearly horizontal for 4' to another 45 and then out of the crawl space nearly horizontal for 4-5' and then drops on a 45 about 6' or so where it Ys into the drain coming out of the basement from the house and then it runs 5' horizontally into the septic tank. Between the first and second 45s is the 1 1/2" Y coming from the sink and the 1 1/2" Y going back up through the floor and a little higher than the toilet tank topped off with an AAV. What sounds unworkable about that set up? I can see all of the plumbing except for the section that dives down to the basement drain and it all is appropriately layed out with properly looking, straight lines and fittings. Your thoughts are greatly appreciated. Most toilets I have seen plumbed usually come down from the floor and turn 90 into a stack or major vertical drop with the venting going on up - I've wondered if the velocity of which this might drop doesn't do something to the air displacement that the AAV can't handle - just questioning the physics of this. Thanks, again for your time.

 

[Tom Sawyer]

quote; There is no such thing as an "air lock"

I hope you are not a plumber if you say that. Of course there are "air locks". That is one of the deficiencies of an AAV, because they CAN create an air lock. When the toilet does not flush, remove one of the AAVs and then try it. If it flushes and/or you feel air pushing OUT of the AAVs connection, then you DO have an air lock, and it is caused by "something" in the line creating a blockage preventing the air from being evacuated ahead of the water.

Yes, I tried to explain that but did a poor job apparently.

 

[Bluebinky]

Could one of you "air lock theorists" explain how air lock works? Perhaps a diagram?

 

[Ballvalve]

One 1-1/2" air valve is too small for a sink and a toilet, one chance. Also a AAV should be very close to the toilet outlet in order to work. You could add a saddle tee [oh, the screams!]

One magic tool for getting crap out of a toilet without removing it is a shop vac. I cannot believe how easy it is to remove a toy or giant turd in just a few seconds with one. Just did a shower trap and got a nice vibrator out of it. Embarassed housewife.