Soil/Waste Stack Offset in HR Buildings
Soil/Waste Stack Offset in HR Buildings
(OP)
Hi
Although this forum is dedicated to HVAC and Refrigeration, however, I think all who are involved in design of building mechancial systems, including plumbing, cross here. So I dare to post my inquiry here.
Have you ever heard or seen of any requirement (as per code or good engineering practice) to offset soil or waste stack in high rise building, say every 10 or 15 floors, to reduce velocity or noise?
Thanks all who share their knowledge in this forum.
Although this forum is dedicated to HVAC and Refrigeration, however, I think all who are involved in design of building mechancial systems, including plumbing, cross here. So I dare to post my inquiry here.
Have you ever heard or seen of any requirement (as per code or good engineering practice) to offset soil or waste stack in high rise building, say every 10 or 15 floors, to reduce velocity or noise?
Thanks all who share their knowledge in this forum.





RE: Soil/Waste Stack Offset in HR Buildings
RE: Soil/Waste Stack Offset in HR Buildings
Thanks for your reply and feedback. I am aware of that part of code dealing with offsets in soil/waste stacks. However, what I am addressing is an arbitrary short offset in a stack actintg as a bumper just to reduce vertical velocity and associated noise. I am wondering about its necessity and ruling criteria here.
RE: Soil/Waste Stack Offset in HR Buildings
Friar Tuck of Sherwood
RE: Soil/Waste Stack Offset in HR Buildings
Thanks. Now I know how it's done in UK. Can I have feedbacks from people who work as per North American or other European codes?
RE: Soil/Waste Stack Offset in HR Buildings
What kind of piping are you using. Typically in applications above, say, two or three branch intervals, cast iron is used just because of the sound issue. If you are using PVC, you will have noise issues. Putting in an offset may help this but you would have to put them in about every 2 or 3 branch intervals.
RE: Soil/Waste Stack Offset in HR Buildings
Friar Tuck of Sherwood
RE: Soil/Waste Stack Offset in HR Buildings
RE: Soil/Waste Stack Offset in HR Buildings
RE: Soil/Waste Stack Offset in HR Buildings
There is no need to have offsets in soils tacks because of the terminal velocity explanation given by PEDARRIN2 I have seen in some high rise buildings(40 &up) two soil stacks with alternate floors connecting to different stacks.This would mean if the main stack chokes,50% of the floors can still operate.I have always connected the last floor(1st floor in Europe and 2nd floor in most other countries) to the main stack with no problems.
RE: Soil/Waste Stack Offset in HR Buildings
However, one must design around the hydraulic jump at the base, as mentioned above.
Tall stacks do create noise, but don't offset the stack, take other sound reduction measures.
cheers,