Cast iron pipe to pvc - connection questions

[mcat]

Hey all,

My kitchen sink no longer drains at all which upon closer investigation looks like it's a cast iron pipe that I believe is just blocked or rusted shut now.
( what initially was thought to be a clogged p-trap, turned out after cleaning, to be a wolverine brass p-trap that had eroded so thin that when cleaning it punched a hole through the thin bottom, which then after repair, was found that the iron pipe is most likely blocked after inspecting the cleanout underneath and seeing it clear up until the top bend down into the cast iron pipe )

My questions are related to how to best approach the replacement of the old iron pipe with schedule 40 pvc pipe.

I was wondering if I can simply cut the iron pipe with a sawzall and clean up the rough exterior so it's smooth and get a rubber coupler and attach to that and then to the pvc? ( part of me says it's not the way to go but would be the easiest and prevent any sewage from coming up if I get too close to the floor )

The other alternative I've read would be to heat up or drill out the lead and pick out the oakum packed in the iron pipe, then hope a local store has some donut that would fit then I could insert the pvc into that and then figure the hookup for the zinc plated vent pipe and copper sink drain to the pvc. If you notice in the above pic, there is a reducer of sorts and I'm wondering if need to keep that or if I would be better served removing that and connecting to the cleanout portion and running a larger pipe?

Lastly, should the sink drain be coming in at the top or should that have been the actual vent pipe and the sink should have come below that? I ask cause it's an old house, 1960's and nothing was seemingly done correct in it


I'm also wondering if I can connect PVC to copper by way of a similar method but with a pvc junction at the top ( images are not mine but for example purposes of a way to connect )

It's been some time since I've tackled a project such as this and the ol' brain isn't what it used to be, so I'm just doing my due diligence and research before I put a blade to the pipe and start hacking away.

 

[wwhitney]

Two comments without addressing your basic question:

1) Any flexible DWV coupling used above grade is required to be the type with a full metal shield.

2) In the second photo the pipe you labeled "vent pipe" doesn't look like a vent pipe. Any vent would need to come off at the same elevation as a trap, and there are no traps connected at that elevation. So I would expect that to be the drain for a different fixture.

Cheers, Wayne

 

[Sponsor]

 

[Jeff H Young]

I dont think the pipe marked vent sounds right either the 45 dosent look like dwv either to me .
but cutting the cast iron and joining with a metal reinforced band is how we do it a mission cp33 or equall

 

[mcat]

The pipe ( zinc plated ) marked vent, runs up into the attic and connects to the main vent that runs out to the roof so that's the vent pipe. The home inspector even referred to it as the vent pipe, it's not hooked up to any other sink or drain.

Looks like cutting the cast iron and using a metal band / c-clamp and rubber sleeve to connect the two will be what I have to do.

 

[wwhitney]

The pipe ( zinc plated ) marked vent, runs up into the attic and connects to the main vent that runs out to the roof so that's the vent pipe. The home inspector even referred to it as the vent pipe, it's not hooked up to any other sink or drain.

FWIW, that's all plausible, but there would be no reason to install such a pipe. So if you're certain it doesn't carry any sink or other drain, most likely it did in the past, and then during a remodel the drain connection was capped off.

Cheers, Wayne

 

[Jeff H Young]

Totaly agree Wayne just see s a red flag a totaly un needed vent and I spot what apears to be a wrong fitting but I suppose its no big deal. that gal pipe isnt a vent for a kitchen above though a kitchen vent might connect to that on way up . the picture is inconclusive of anything going on with the kitchen.
based on info I have replacing the cast with pvc or abs down to the cleanout area might be good idea I suppose dont worry about the gal pipe you dont have concern nor I probebly not hurting anything but id be curious but you arent thats ok