DWV design OK?

I'm about to tackle the next phase of an incorrectly plumbed drain and vent for two sinks. Attached are diagrams of the current configuration and two proposed configurations.

I think the current configuration is wrong b/c the more distant laundry room sink does not have an independent vent. Furthermore, I think the galvanized 1.5" circuit vent is redundant with the AAV.

My main goal in re-doing this section of plumbing is to provide independent venting of the laundry room sink. I'd also like to replace the AAV, since I don't think it is necessary.

I'd appreciate comments from this forum on my assessment of the problem and on my proposed solutions.

l

There are better easier ways to do it, but you can not have the rise with the two 45's on that last sink without venting it also. You do not need that first vent on the left unless it is a really long run. The vent cannot go horizontal until it is 6" above the flood rim. Is this some kind of island or what?

construct30 said:

There are better easier ways to do it, but you can not have the rise with the two 45's on that last sink without venting it also.

Click to expand...

If the new vertical vent line was upstream from the rise would it be OK? or do I need two vents when there is a rise?

Also, can you briefly describe your ideas on better easier solutions?

l

p.s. Did you look at all three diagrams?

Is there a wall behind the counter? Is it a double vanity?

I think you use UPC code correct?

Not a double vanity

construct30 said:

Is there a wall behind the counter? Is it a double vanity?

Click to expand...

Not a double vanity. There is a wall behind the counter. The sink that is vented under the counter is actually on the other side of a wall in a bathroom. (The sink on the far right is a shallow utility sink mounted in the countertop on the near side of the wall.)

I think UPC is correct for Seattle, Washington, where I live.

Yes

construct30 said:

I think you use UPC code correct?

Click to expand...

I think so.

I take it you have to keep the horizontal vent pipe off the stack at that height. It is too low to meet code. It should be at least 6" above the counter.

Come off the main drain, put your wye then to a 90. Then bring both up to the sanitary tee, then bring the vent straight across, preferably higher, then use a tee on the first drain and a 90 down to the second, like a ladder.

I am more familiar with IPC, but UPC is even tougher on venting.

I hope that made sense.

Plan view and more questions

construct30 said:

I take it you have to keep the horizontal vent pipe off the stack at that height. It is too low to meet code. It should be at least 6" above the counter.

Come off the main drain, put your wye then to a 90. Then bring both up to the sanitary tee, then bring the vent straight across, preferably higher, then use a tee on the first drain and a 90 down to the second, like a ladder.

I am more familiar with IPC, but UPC is even tougher on venting.

I hope that made sense.

Click to expand...

Thanks for your comments. The sad thing is this is all plumbed IN FRONT OF THE WALLS (see plan view, below).

The wall behind the counter is a partition that is studded with the 2 x 4s on their sides, so even 1.5 pipe fittings won't fit inside it. Consequently, it would be nice to keep the venting below the counter...maybe that's why the guy used an AAV? Could I use the type of venting used for a sink on an island?

Also, the drain and vent pipes go around an inside corner and remain outside the wall b/c the vent stack and soil pipe are 15" out in the floor. I can't relocate them inside this wall b/c it is concrete up to about 3'. The counter doesn't turn the corner, and the washer and dryer sit in front of the pipes.

Thanks.
l

OK I kind of get it now. When we have windows and such we go as high as we can so under the circumstances, I guess you have to do the best you can. Terry has posted lay outs for the island vents for UPC. I think you are better off with what you have planned than using the island vent, but that is just my opinion.

UPC island vents are a bit more complicated and work better. The IRC allows for just a squared loop vent which is easier. I personally think in your case going up as high as you can is better than the loop going back down.

I would make that top vent pipe straight though with just the one tee going down and the 90 going down at the end. IMO a vent works better with less offsets You must still maintain a minimum slope. Thats why you need the sanitary tee out of the wall and the vent coming off the top. The vent becomes usless if the bottom of the pipe outlet rises higher than the opening of the pipe at the vent, so you don't want to use a wye out of the wall off the vent stack, even though many diagrams in this forum show that, it is technically incorrect, or like in your case you had the two 45's after the vent.

Many times even though it is not up to code, you have to improvise and do the best you can and it will usually work as long as you have a basic grasp of how a vent works. What you have planned is way better than using the AAV, if you think about it logically.

You can work in more absolutes when building new as apposed to remodeling and most inspectors even recognize that.

Revised proposal--any more comments?

Thanks for your very helpful comments, construct30. Here's how I plan to do it:

How about like this? The vent needs to get above the flood rim before going horizontal and the vent needs to be above the 45's.

Redwood said:

How about like this? The vent needs to get above the flood rim before going horizontal and the vent needs to be above the 45's.

Click to expand...

The vent needs to be above the 45's like redwood says Which if he looked at the last post by lottia he would see that is how it is, or just use elbow at end of drain and go up to sanitary tee and on up to vent.

Redwood, read the rest of the posts, the wall is not deep enough to run the vent. The vent needs to stay in the cabinet, special circumstances. It is that or run an island vent, IMO running the vent in the cabinet as high as possible is better than going down or leaving the AAV. Not exactly to code, but the only fix is a major remodel to make the wall deeper. It is a remodel, not new construction.

construct30 said:

use elbow at end of drain and go up to sanitary tee and on up to vent.

Click to expand...

Like this? Also, note the two questions in the new diagram:
1. does a sanitary-tee with 1.5" on top and side, 2" on bottom exist?
2. Can I use a large-radius 90 below the santee?

Thanks
l

construct30 said:

The vent needs to be above the 45's like redwood says Which if he looked at the last post by lottia he would see that is how it is, or just use elbow at end of drain and go up to sanitary tee and on up to vent.

Redwood, read the rest of the posts, the wall is not deep enough to run the vent. The vent needs to stay in the cabinet, special circumstances. It is that or run an island vent, IMO running the vent in the cabinet as high as possible is better than going down or leaving the AAV. Not exactly to code, but the only fix is a major remodel to make the wall deeper. It is a remodel, not new construction.

Click to expand...

Unfortunately at 10:58 P.M. Iwas putting my post together and did not have the luxury of seeing the last post yet. What kind of distance are we talking about to this upper 45 from the vertical pipe in the wall. The vent cannot go flat below the flood rim as drawn. Can it run at a 45 to the vertical vent? Building a higher partition to enclose the vent should b e looked into. I doubt the inspector would buy a loop vent in this situation.

It would be possible, but very, very ugly to build an enclosure for the vent above the counter, which has an integrated backsplash.

The 45 slope could begin only after we're out from under the counter, b/c there's a window in the ext wall at the end of the counter, and washer dryer need to go in the ell between the counter and the ext wall.

That said, would it help to have the connection to the vertical vent pipe be above the countertop? That would be doable.

In the end your comments make me think it would be best not to try to correct the bad plumbing job done by a so-called pro 10+ years ago! I may not be able to make it any better.

l

I guess logically I can not see how an AAV and the vent now can be as good as a vent run as high as it can under the counter. It would be the same idea or better than an island vent. If an AAV would work then the loop under the counter would work except under flood conditions.

You could run it past the local plumbing inspector and see what they say. Where I live we run into a lot of odd situation and inspectors try to work with the situation. They would like the loop more than the AAV.

Ideally on one side or the other you would add studs to make the wall deep enough and the put the cabinets back, but if that is not doable then I would go for the loop vent as high as possible under the counter. They do it all the time when there is a large window at the counter level.

We discussed the issue of the window in another thread and Terry responded that he would run as high as possible rather than use an island vent. Logically it makes sense, it is the same idea only higher, which should work better.