We are remodeling our kitchen (gutting it) and intend to install a hood vent that requires an 8" round duct or 50 sq inches of area. However, several problems have been encountered. Picture 1 shows the location of the cooktop...it will be in front of the 2nd floor heat duct you see running up the wall. That heat duct goes up behind the wood and then curves under the floor and runs to the outside wall in the room behind this wall.

1. The interior depth of the wall behind the cooktop is only 5-3/8" (between drywall). This means we cannot fit an 8" round pipe in the wall. (The width between studs is 14-1/2".) [Picture 1]


2. To add to that, in the same wall bay the venting for the vent hood would have gone up is a heat duct to the 2nd floor.


3. Next, the bay in the ceiling the vent duct needs to traverse to get to an exterior wall is blocked by an upstairs shower drain pipe. [Picture 5]

If we cannot move the shower drain pipe then we will be forced into using a recirculating vent hood.

We have had 2 master plumbers out to give us an estimate for moving the shower drain pipe. We received 2 very different estimates reflecting 2 very different approaches.

The first estimate was for $4,800. It involved moving the shower drain pipe to meet the main waste pipe & moving that drain's vent to the right and going up an interior wall into the attic and out the roof. This estimate included knocking a hole in one of the bathroom walls on the second floor, going through the roof, and, when done, leaving the partially demolished wall paint-ready.

The second estimate was for $700 ($550 for work + $150 for the permit). It involved moving the shower's drain pipe to join the toilet's waste pipe. The plan is to remove the elbow [Picture 4] and replace it with [now here’s where I’m unclear] with a special ??? (Tee something?) pipe that would join the waste pipes (shower & toilet). The shower's drain/waste pipe would turn 90^o toward the inside, run up the edge of that bay and then a hole would be cut through the joist to allow the drain pipe to join the toilet waste pipe. No new vent would be required because of the existing vent.

Obviously, we prefer the second estimate due to the price. However, will there be a problem with the toilet's waste backing up into the shower with the second solution? The plumber assured us there would be no backup when there's water flowing through both and when there's only water going through the toilet waste pipe. But, I would like another opinion...but do not know of another plumber we can get out here on short notice (we live out in the boondocks). Our project has been on a stop work order for almost 2 weeks now and we have to make a decision Thursday or Friday. So, I'm hoping some of the plumbing experts here can help me. I hope I've given you enough details and pictures to help me. Let me know if there's any other information you need!

Thanks in advance!!

Picture 1: Wall Where Vent Hood Is Needed (in front of bay with heat duct)

Picture 2: Toilet Waste Pipe Overview

Picture 3: Toilet Waste Pipe Joins Main 2nd Floor Waste Pipe

Picture 4: Toilet Waste Pipe and Waste Pipe Vent Closeup

Picture 5: Shower Drain Pipe Crossing Needed Bay

Picture 6: Shower Drain Pipe Closeup

The pipe going to the left would be turned 90^o (towards us) and stay in the bay it started in until it joins the toilet waste pipe in the next bay over to the right.

* We can't go under the floor since all the bays that we could use are also full
* We can't move the cooktop since no other bay is open...they all have something blocking either the bay run, the end of the bay, or the beginning of the bay
* We can't move any of the gray piping since it no longer meets county code and as long as we don't touch it we don't have to change it out...once we touch it it becomes an even greater issue of replacing all "touched" piping (from input to output)

These two solutions seem to be the only ones available to us.

Why am I questioning the second solution? The first estimate came from the plumber who is subcontracting to our GC for the kitchen work. We were told, initially, that he had two options...the one we got the $4,800 estimate on and a second option that was pretty close to what the second plumber gave us. However, we cannot deal directly w/the first plumber but have to go through the GC. The GC only gave us the first solution. When I asked what happened to the second option, he said there was no second option.

So, we brought in a master plumber who we have worked with in the past on our well pump, hot water heater, and well holding tank..we've been happy w/his work. He gave us the second estimate ($700).

When I told our GC that we had a second estimate done and that we would be going with him if we can solve one other issue, the GC started talking about toilet waste backing up into the shower drain. So, we called the second plumber and he insisted that would not happen--he described his plan but the GC wasn't convinced...so he's going to call his plumber (the one w/the first estimate) to verify that it will work.

At this point, I don't trust our GC...I'm sorry to say this, but I no longer feel confident that he's being up-front with us.

I should note that our KD, who works w/the GC, even told us to go ahead and use the second plumber if we got a better solution or price from him.

So...I was hoping I could get some information from the experts on this site!

As to building out the wall...we are considering building out the wall w/the cooktop 6" to provide room for the hood duct work to get to the bay. Vent-A-Hood has a "connector" that converts an 8" round duct to a 6"x8-1/2" rectangular vent so it will fit in the ceiling since the plenum is only 7-1/4" deep (depth b/w the floor upstairs and the kitchen ceiling). There appear to have been many things done differently than the norm when this house was built!

The downside to this is that it reduces the aisle clearance b/w our peninsula and refrigerator to 34"...a rather tight fit! So, while we wait for the estimate on the wall (due after lunch) and mull over the aisle issue, I'm trying to gather more information on the plumbing issue!

Are you at least thinking about a replacement for the grey pipe down the line? PB pipe is failure-prone.. if you stay in your house long enough, you'll probably have to replace it, and if you sell it's something a home inspector will probably flag. PB pipe is the "aluminum wiring" of plumbing - it's no longer code for a good reason, and although it's not an immediate hazard if in good shape, it is something you will have to address eventually.

I did respond to my thoughts in your other post about connecting the shower to the toilet.

For the other price, you should be able to remove and repipe all of the plumbing :).

However, this does bring up an interesting thought, Can this horizonal waste pipe be split so that it no longer runs over the "vent area". You cut out the horizontal line between the toilet line and the tub line. Rach of these then runs down to the basement and then connects to a horizontal line, connecting the two in the basement. Not sure if there is room in the basement to do that. When looking at the pic of the wall where the vent hood will be, there is 2 2" pipes that run down the wall and one of them looks like it comes out of the wall at the botom of the pic. There isn't another pic so not sure wht that is for or where it connects to.

You might be able to get a plumber to re-route the main horizonal stack, like I mentioned above and then have no need for the built out wall. This may cost more $$ but you then don't loose floor space either. Maybe worth considering.

The first thing you say is that you can't fit the 8" round pipe in the stud cavity, true that, but you can go to a rectangular duct, they make em just for your application, to fit in a stud bay.

It looks like the shower drain could be reconfigured so the horizontal section of pipe is higher up in the joist bay allowing the duct to pass underneath.

Have you had a HVAC man look at this ? Perhaps he can work the sheetmetal in a way so you won't have to bother moving plumbing

If that still won't work, yes you can tie in any and all the other drains into the toilet line so long as it's tied in downstream of the toilet vent.

It's only the toilet line from the toilet to the vent, after that it's just a drain line.

No matter what the configuration, if it backs up it will be visible first at the lowest point, usually the shower or tub.

Sorethumbs...I'm sorry, but I don't know what you mean. The pictures show our current plumbing configuration.

Houndhandler...The space b/w the 2nd story floor and the kitchen ceiling is only 7-1/2" so if we have a 6" x 8-1/2" rectangular duct, there will only be ~1-1/2" below the duct. The pipes are wider than that. Yes, an HVAC specialist did come out and he said if we re-routed the drain pipe he could create a duct for us that would fit in the bay as well as fit under the facia (?) on the outside wall that's holding up our 2nd floor (extends approx 3' beyond the first floor).

You said the other drains have to be downstream from the toilet vent...the plumber was talking about tapping in upstream of the toilet waste pipe (pictures 2 & 4 show the toilet waste pipe). He was going to replace the big elbow with a special T of some kind and the shower drain would drain into that T. It sounds like that shouldn't be done since the vent is downstream from this proposed T.

We had another plumber out who seemed completely clueless...so we're looking for another one--tough since we're in a rural area!

First off, thank you all for your comments and suggestions. I thought you'd like to know the final outcome of our plumbing & venting issues....

We have moved the shower drain pipe. After getting a totally unacceptable estimate of $4,800 to move our shower drain pipe & vent from our kitchen contractor that included punching a hole in the roof to vent the drain, we solicited comments and estimates from 3 outside plumbers. Of those 3, 2 proposed the same solution and a third proposed a different solution...none of these solutions involved punching a hole in the roof. Why not? Well, it turns out we have a whole-house vent stack in the attic that we can tap into. All 3 outside plumbers checked our attic to see if we had one and then proposed solutions using that vent stack. Our kitchen contractor's plumber never checked the attic for that stack so assumed he would have to go through the roof. (You know ASSUME does...)

Our first outside plumber proposed tapping into the toilet waste pipe. But, all of the other plumbers were uncertain if that would pass code...this estimate was for $550 + $150 for an express permit

The other two plumbers proposed rerouting the shower drain back to the main 2nd floor waste pipe...one was for $925 and the other for $1,000 both + cost of drywall repair.

We went with the $925 estimate for a couple of reasons...(1) they were local and have an "A" rating across the board on Angie's List (the first time it's been useful!) and (2) the other plumber was not a master plumber (journeyman), he was not insured, and wasn't even sure if his license was up-to-date in our county...all red flags to us.

Anyway, so our plumber came out and moved the drain pipe. He then told us he would try to run the vent to the attic without cutting into the wall (saving us the $500 for drywall repair). It worked! He was able to push the vent pipe up the wall and into the attic without any problems.

While he was working on this we asked him about the Polybutelyne water pipes...he, as well as all the other plumbers, had recommended changing them out. We're on well water so there's no chlorine involved, but they did tell us that it would eventually become brittle and split. So, we got estimates for that and, since our kitchen project has been stalled for over 8 weeks, went ahead and had it done ($3,200 for replacing water pipes + $1,900 to repair drywall in 3 bedrooms + LR textured ceiling = $5,100. We already have the ceiling down in the kitchen and the main wall opened up so no charge for repairing those)

This was all done fairly quickly and we have had both our final inspection done and the drywall repairs completed...in time for our kitchen to restart Wednesday.

The only drawback...previously, since each fixture had it's own water pipe, flushing the toilet had no affect on the shower. Now, however....a very different story! It's taking some getting used to!

BTW...it turns out the first plumber's solution would have met code and passed inspection since he had planned to use a sanitary T. I was curious so I asked the inspector about it when he was out Friday.

If you want pictures, let me know and I'll post them.

Thanks again everyone!