View Full Version : Toilet with Loop Vent

06-12-2006, 04:36 PM
Can I use a loop vent for a toilet? I have a situation that does not lend itself to a standard vertical vent. I want to use a 2" loop vent. Right now I will have a shower, toilet and sick connected to this loop vent.


06-12-2006, 04:52 PM
I've never seen an inspector that would allow a loop vent for a toilet.

Maybe a kitchen sink, with a foot vent off of the loop, buy not a toilet.

06-12-2006, 05:05 PM
I have not found any examples of using a loop vent for a toilet. However, technically, I can not think of a reason it would not be acceptable. My main waste line is 3" and I plan to run a 2" loop vent configuration.

Gary Swart
06-12-2006, 05:45 PM
Hmm! Consider this, it matters not what you think, it matters what the inspector thinks.

06-12-2006, 07:41 PM
Gary, I appreciate your candor. However, I am trying to educate myself on why certain routings are acceptable or not. I guess I've learned over the years to not accept what someone says without first understanding why it needs to be that way. As a kid, I use to always hate adults saying, ..."It's that way because I say so." I guess I thought this was a forum to educate us less fortunate ones. Maybe I'm wrong. So give me a little credit for asking a good technical question that I would like a technical reason why it will not work.

So, anyone else out there that can shed some light on this I would appreciate it. I know codes are somewhat different in different states, so if you have a specific state code that does not allow this, I would like to hear about it.


06-13-2006, 05:12 PM
Just wondering. Can anyone describe one?

06-13-2006, 08:04 PM
The only place I have seen a loop vent approved is on an island, where there simply is no wall to take the vent up into. Since this situation (no wall) is unlikely with a toilet, I think you would have to do some fancy talking to get it approved.

06-14-2006, 02:15 AM
running an island vent for a toilet makes no sense. You still need to run a foot vent off and island vent, in which case you can vent the toilet in the usual manner. The vent for a toilet comes off the drain below the floor and can run to any wall. The foot vent for an island fixture also comes off below the floor. Running an island vent is not practical for a toilet.

06-14-2006, 10:03 AM
If I take the configuration for a loop vent for an island, and substitute a toilet for the sink, the toilet drain and vent will be below the floor and will run parallel to the joist to the outside wall where the vent turns up and the drain turns down. If I can vent a sink this way, what prevents me from venting the toilet?

I know this may seem like a crazy thing to do as I am able to run a conventional vent but I am trying to get creative with my plumbing to minimize penetrations through the roof, especially since I am the one that will have to get up there to complete the flashing. If I run the vent straight up, then I am towards the top of a 45 degree sloped roof. If I can use a Loop vent, then I can tie this vent into another vent line which is located towards the eaves, which reduces my velocity if I fall off the roof.

It is not tha fall that hurts, its the sudden stop.


06-14-2006, 07:11 PM
According to the IPC you can configure your DWV for this fixture group with an AAV (air admitance valve)you must have access to the AAV for it is a mechanical device that could fail and would need to be changed in the future.The AAV eliminates having to vent thru the roof,which I think solves your problem,check with your local plumbing inspector.

06-19-2006, 12:38 PM
IF done properly, and that is the key word, it will work, but why are you making your life so difficult? If you have another vent through the roof at the eaves, just connect the conventional toilet vent to it, in the attic, before it goes out the roof. The problem with a loop vent is that it does not always function as a proper vent until towards the end of the drainage cycle. With a toilet, which creates a substantial suction due to its volume of water, it could affect the traps in the other fixtures. And in any case, a loop vent is for an individual fixture, not a group of fixtures.