Is there another way of attacking the problem? Can the 2 1 1/2 pvc pipes be moved to the same bay as the heat duct....then in the vacant bay run the range top vent? Rather than a 8" round vent you might get the same volume with a recetangular vent.
Can the wall be built out to allow enough space in the bay that you want for a rectangular vent?
And if the 2nd bidder is a licensed plumber and says that his plan meets the code, I don't see what the problem is.

Thanks Coolvt. Another solution LOL!! We've been trying to find a solution to this problem for over two weeks now!

* 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!

The plumbing code is quite conservative about DWV stuff. If it passes code - and since plumber #2 is pulling a permit, they obviously intend to pass code - it ought to be fine.

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.

Buehl,

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.

In the pics, the 3" or 4" horizontal drain has sanitary tee's laid on their back. It appears that the tee's receive branch drains - Is that ok? to code?

I'm having a little trouble visualizing the configuration but,

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.

Thanks for still helping...we haven't decided if we should go ahead with this yet since we're unsure of the feasibility of the plumber's plan. [He is a master plumber, licensed, and knows we're doing this w/a permit and that it will be inspected by the county. He's worked on our well & replaced our water heater & well holding tank, but we've never had him do this kind of work before.]

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!

Standard in the wall rectangular ducting comes in 3 1/2x14 which equals 49 sq in. Would that be close enough and leave lots of room in the bay?

I don't think so. Our ceiling bay is 14" wide by hmmm...7" deep...I thought our GC told us 7-1/2"...I just measured it and it's only 7" deep. I was told that you do not want the duct to fill the bay width-wise b/c then the ductwork will be jammed against the joists on either side and the vent fan will be louder due, I think he said, to the duct vibration on the joists.

I would not be too concerned with vibration, ductwork will be attached to framing in lots of other points.
Brings to mind just how long is the ductwork going to be ? You may find that if you start adding lots of elbows and lengths the hood maker may spec a larger duct. Especially true with ventahood.
TBS, I would not even consider a recirculation system.
There are other brand hoods that spec a smaller duct.
If the joist bay is 14X7 the shower pipe is about 2 1/2" dia. leaving about 5" X 14" for the duct, that's 70 square inches.
I don't see a vent for the shower ?
Yes those are santees on their back, not code.
If the plumber is talking about installing a low heel inlet in place of the closet ell then that is not code either.
At least not UPC code, I understand many areas now use international building code so rules may be different.
Every fixture needs a vent, from the toilet to it's vent is called the waste arm. After that it's just a branch drain.

UPDATE...

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!