wrote in message
oups.com...
Building a new house and my upstairs bathroom is directly over the
dining room. I'm a little concerned about the noise of a flushing
toilet (and a draining pipe) invading the quiet of the dining room. I
am assumming that most of the noise of a draining pipe comes from when
the water changes from horizontal to vertical (between floors) and
splashes at the bottom. (Is this true?) The toilet is near the wall
separating the dining room and kitchen. I could bring it down this
wall, or I could divert the toilet waste parallel to this wall and
bring the water down the wall separating the panty and the dining room.
This pantry wall is ideal because the presence of a built-in china
cabinet will certainly reduce the amount of noise coming from the pipe.
However to get to this wall I have to cut through six or seven 2x
10"s on 16" center (the pipe would be running perpendicular to the
floor joists). Cutting 4" holes on 2 x 10's just doesn't sound like a
good idea.

Also, am I fooling myself? Is running the horizontal pipe in the
ceiling for an extra 8' to get to the pantry wall a good idea versus
going directly to the closest wall and dropping it there? I am
looking for suggestions.

Here are the ones that I have heard:
1. Replace waste pipe with cast iron - cast iron is quieter - don't
like that idea - really like the ease of PVC - do not like the weight
of cast iron. However, if I do put in cast iron, how much? From the
closet bend to the crawl space?
2. I have also been told that I could add steel plates to the 2x10's
and stiffen up the joists which would allow me to drill the holes with
confidence.

Are there any other good ways to insulate and negate the sound? All
comments appreciated.

Thanks.......rwm

Lets get real here. You were actually considering cutting almost 1/2 way
though 6-7 joists just to avoid some sound. You will have a lot bigger
problems if you do that.
Not only will you lose much of the structure you also will have a horizontal
run susceptible to blockage. Just dump it down the wall. Fill the cavity,
around the pipe, with foam if the sound is going to bother you that much.