Wet venting should be avoided in this instance...the guys trying to save you
a few bucks will end up screwing you.

Plumbing is broken into two areas, that which is seen and that which
carries. A contractor willing to cut corners and ignore code will not save
you money...and the plumbing inspector will not allow the wet vent. BTW,
wet venting is intended to vent closely adjacent fixtures, not those on
seperate levels, i.e., a sink can be used to wet vent a toilet or a shower,
however, a toilet can never be used to wet vent another DFU. The two cheap
quotes are attempting to use a toilet to wet vent other fixtures.
"Andy Hill" wrote in message
...
Peter Langevin wrote:
I live in a 1 1/2 story home, one bathroom on the first floor. I had
a remodeling contractor out last week to give me an estimate to add a
second bathroom to the upstairs bedroom. His quote came back
significantly ($5000) higher than the other 2 I got, and when I asked
him what the difference was he said it was due to a "wet venting
issue." I mentioned that 2 other contractors hadn't mentioned it,
and he essentially told me that they didn't know what they were doing.

I'd like to see who is "all wet" so I know who to believe. The layout
is pretty simple and to the best of my notes I'll try to recall what
the last guy said.

I have a single bathroom (tub/lav/toilet) on the first floor, as well
as a kitchen sink and dishwasher. A single 3" PVC pipe is used for
the drain on all of those items, and it extends straight up through
the roof without anything else connecting to it.

The bathroom on the second floor would be right next to the 3" pipe,
and the other contractors said they could just drain right into it,
and that it would also serve as the vent, as long as everything was
within 5' of it upstairs.

The last guy said that you can't drain fixtures from the second floor
into the same drain used for the first floor, since the first floor
fixtures are being "wet vented" into that pipe. To add the bathroom
upstairs would mean that you would have fixtures "wet vented" above
others that were also "wet vented." This contractor says the extra $$
is to add a second 3" PVC drain all the way to the basement and extend
it through the roof. When I spoke to the first 2 contractors they
told me that he was nuts, and that they could absolutely be vented and
drained into the same "stack" and that the "DFUs" were not exceeded.
No idea what a DFU is.

So, help! Who is correct? Can I add the second bathroom upstairs
with the same vent/waste pipe?

DFU = "Drainage Fixture Unit"

It's been a couple of years since I've had to deal with this, but last
time I
checked most residential codes only allow wet venting for fixtures on the
same
floor, so if they're planning on just dumping the 2nd story waste into the
existing vent stack, that's a no-no.

That's not to say that a new soil stack all the way to basement is
needed -- if
the existing soil stack (and associated vent stack) is big enough (that's
where
the DFU issue comes in), then it might be possible to use the existing
vent
stack as the 2nd story soil stack (sliced off accordingly), and run a new
vent
stack (starting at the existing hole in the roof). down to the 2nd and 1st
floors.

I'm not a plumber by trade, 'tho, so something may've changed in one of
the
codes in the last couple of years.