As a side note, if I want to get rid of the cast iron altogether and replace it with plastic (sorry Sylvan!), what are the chances the cast iron is supported inside the wall of my one-story house? It can’t be as easy as cutting it loose in the attic at the top of the wall and having it fall to the floor in the basement. Can it? [/B][/QUOTE]
For a one family home owner hell bent on using plastic for drainage no problem.
As for the cast Iron stack falling YES it can if you just cut it out.
What normally holds these stacks in place is “Riser clamps” sometimes called pipe rests.
On the horizontal we use clevis hangers.
Try to expose as much as the cast Iron as possible and then start removing it from the top and replacing with PVC.
The use of “Fernco” fittings and couplings are NOT allowed in some areas by code as the folks who do use it cannot depend on their skill to cut a pipe properly or line up piping in a skilled craftsmanship manner.
You see the Fernco is just a piece of rubber with 2 hose type worm clamps subject to sagging and splitting.
For example a plumber in my area using this type of connection can have his/her license revoked (and rightfully so) and a fine is in order if nothing else for not knowing the code.
Check out the folks at home centers and plumbers lacking skills and see the materials they buy.
What I would suggest is following the “basic” plumbing design as follows
Every change of direction greater then 45 Degrees instal a clean out
At the base of every stack instal a clean out
All clean outs should be full size up to 4″ piping
Use long radius fittings as much as possible and limit 1/4 bends (90 degree short radius ells) to go from horizontal to vertical.
Consider the following option for the best of both worlds.
Use Charlotte pipe for the cast Iron drainage and Charlotte PVC for all your venting using no hub or mission couplings
This will give you a great job and will save you some time.
Remember if your going to use plastic read the precautions 1st like carcinogenic fumes eye protection gloves etc.
The stumble bums I saw using plastic never read MSDS or OSHA or NIOSH.
They just go about their merry way not knowing about codes as they learned strictly OJT
THERE IS NOTHING wrong with PVC drainage BUT my personal choice when conditions allow is copper type L tubing for all above ground work including heating and Type K copper for all under ground and Cast Iron for drainage.
When you do this job think like a professional to protect your investment.
Use clevis hangers and forget band iron, Use riser clamps for the vertical lines and on the horizontal figure a clevis hanger every 5 feet.
If you need to fine tune your specifications just send me an E mail.
Check what code your using and any local amendments to it.
We can discuss sizing and pitch and NO WET Venting pleaseeeeeeeeeee
Lets try to make this a work of art THEN when your master piece is completed take some pictures and we can set up a “plumbing franchise” in your area and ILL take the local mater plumbers test and you can run the operation there ROFLMAO