Replace All Cast Iron Plumbing - DIY?

Hello forum,

I'm considering taking on a rather large project here and I'm wondering if it's possible to do this on my own. What I have is a 1948 Cape with 1 full bath (upstairs) and 1/2 bath downstairs. In order to get to the stack, I will have to demo 1 wall in the 1/2 bath downstairs, and the upstairs full bath. The full bath is directly on top of the 1/2 bath, with the main stack running straight up, right behind the toilets. I'm not planning on tearing up the basement floor at this point, so the PVC would tie in just above the basement floor.

Most of the issues I'm having at this point are coming from the full bath on the second floor. The shower drain tends to back up quite often. I've snaked it out several times, and that will be good for a few months, then it starts to back up (usually with hair). The sink has the same problem, and neither of these are properly vented. The sink makes a terrible bubbling/gurgling noise when draining as it gasps for air.

So, from the roof I want to remove all the cast iron, and replace with PVC all the way down to the basement where it ties into the cast just above the floor. While the wall is opened up, I'm going to replace the copper with PEX. There was a galvanized nipple for the upstairs bathroom sink that already leaked and destroyed the wall behind the vanity. That post is here:

Leaking Sink Supply Lines

I think I can do all the PEX, but I'm wondering if the cast iron replacement is too much for me to handle. I wouldn't mind doing all the demo work and have a licensed plumber come in and do all the PVC work, but I have yet to find someone I trust around here (NH). Any thoughts? I appreciate any direction/advice.

I would say you could handle it (depending on your skill level i suppose) but it will probably be a lot of work for you. The main thing is just knowing the codes and knowing which fittings to use where.

Thanks for the reply. I think what I'll do is post a few pictures when I open things up and see what it looks like.

There are a lot of post on this topic here. venting seems to be the most discussed. Try searching and see what you come up with. You can probably reuse the existing vents and just replace using the same configuration . It's when you try to add or change the layout when it gets confusing.

Mr_David said:

There are a lot of post on this topic here. venting seems to be the most discussed. Try searching and see what you come up with. You can probably reuse the existing vents and just replace using the same configuration . It's when you try to add or change the layout when it gets confusing.

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Mr_David,

Thanks for the reply. The problem with the existing Cast Iron is... NO VENTING! I don't think anyone cared about venting in the late 40's when this home was built. Everything seems to share the main stack as a vent, going out through the roof. Well, everything except the basement utility sink which has a "New Hampshire Valve" (AAV) as my neighbor calls it (MA plumber). I'm going to have to vent everything properly when doing this project, and that's where I will get hung up I'm sure. I understand what needs to be done, but the different fittings are very confusing to me. I'm going to add a few pictures here to start very soon.

Let me give you all an idea what I'm dealing with here, which I suppose is nothing new to the pros on this site. Here's where I want to tie in with the PVC in the basement, just above the cleanout here:


(ignore that corrugated pipe in the background)

I'm guessing there's a PVC adapter that will fit right into that hub, and make a clean transition from cast iron (Fernco? If you know the part, please let me know!). I'm debating whether or not to add a washing machine discharge line here, or keep draining it into the utility sink. I do like how it keeps the sink trap primed, so I might leave it.

Here's a pic where it all turns, and heads upstairs:


Finally, here's an example of what I expect to run into when I open up the walls:


This is the spot where the galvanized nipples leaked and destroyed the wall. luckily it's behind the vanity, so nobody sees it. To me, that seems like an awfully steep drop on that pipe, and the sink makes terrible gurgling noises when draining. Notice the copper lines feeding up to the sink. Back in the late 40's, plumbers would use their teeth and bare hands to bend this copper. No 90s or 45s around. Awesome!

First Photo

You can cut pipe between the hubs. But old cast iron was truly cast.
As depicted by the red circle the outside of the pipe often not truly round because of the casting forms. You can smooth this out with a grinder so you can use a band seal fitting. but there is probably another grove on the opposite side as well. If you plan on removing the cleanout as well, you can drill out the lead and install a new pc of pipe into the hub in the concrete, Just be carful not to crack the hub. OR leave the clean out and remove the lead from the hub ontop of C.O. That way if you mess up you have a second shot at the bottom hub Look at my thread on how to replace cast iron flange. shows you how to remove the lead.

Lead in a short pc of new no hub soil pipe and connect PVC with a NO hub X PVC adapterand No-hub coupling or a Mission Band.

Do Not Use a Fernco fitting. Does NOT have a band to keep the pipes aligned

Mr_David!

I was reading your post in great detail just a few days ago! I really like what you did with that toilet flange, but I don't have any oakum and lead wool - I wouldn't even know where to get that material! Drilling out the material is exactly what I was planning on doing, but instead of the band I was thinking of using this (donut, not Fernco?):



Of course, I would really spend my time cleaning up the cast iron either way, so both would work I suppose. Are you saying I should drill out the hub, as you did in your wonderful tutorial, and "lead in" a small section of of PVC, and then connect it to the rest of the plumbing with the no-hub adapter and mission band? Got it.

I have never used a gasket like that but it might be an Okay alternative. Frodo or someone else may have some insight on this.

If you pack in a new pc into the hub I would try to get a new piece of cast iron No HUB soil pipe, the use the adapter with a no hub coupling OR just a mission band
Mission bands will work on plastic to N.H. pipe without the adapter . There is a small difference in O.D. size in pipe. That's why you use an adapter with the NO-HUB coupling.
If you try to pack a pc of PVC into hub it may distort and become loose over time. I generally work with ABS here for drains and Not PVC.

I have heard some may use an epoxy seal to seal the new pipe into the old hub But Not sure if that works.

Solid said:

Drilling out the material is exactly what I was planning on doing, but instead of the band I was thinking of using this (donut, not Fernco?):

Of course, I would really spend my time cleaning up the cast iron either way, so both would work I suppose. Are you saying I should drill out the hub, as you did in your wonderful tutorial, and "lead in" a small section of of PVC, and then connect it to the rest of the plumbing with the no-hub adapter and mission band? Got it.

Click to expand...

Here is more info on the spout seal- -FERNCO Sewer Pipe Compression Joint Sealers-

If you do decide to remove all of that cast, you must support each section as it will come down on your head. Ask me how I know...

Thank you KULTULZ. You aren't kidding - this stuff is HEAVY! I had to repair/replace a small 2" section that was buried under the floor in the basement, and just that small 3' section was a bomb. I can't even imagine how much the section in the basement weighs! I guess I would have no other choice but to start from the top and break pieces off as I go down through the wall. Unless I try to support it from below, I don't see any other way.

About these donuts... The mfg says that you can send in your dimensions and they will get you one that is an exact fit. The problem is I can't really measure this accurately until I pull it all apart. I'm just guessing, but I assume this is 4" (I'm at work now, so I can't measure)? Is there a range of sizes I could order in advance so I'm ready to go when things come apart? I suppose I will need the ID of the hub, depth of the hub, and OD of the new PVC that will fit inside?

Solid said:

About these donuts... The mfg says that you can send in your dimensions and they will get you one that is an exact fit. The problem is I can't really measure this accurately until I pull it all apart. I'm just guessing, but I assume this is 4" (I'm at work now, so I can't measure)? Is there a range of sizes I could order in advance so I'm ready to go when things come apart? I suppose I will need the ID of the hub, depth of the hub, and OD of the new PVC that will fit inside?

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This is the problem with old cast and has been mentioned previously, you do not know the quality and conciseness of the hub casting until you get there. This is why they make so many different sizes and even then you may not get a good seal.

Have you thought of just replacing those sections as needed in PVC/ABF? Additionally, PVC (use solid core as a minimum) will not contain sound as well as cast, something to think about while hosting a dinner party...

-The Quiet House® System - CHARLOTTE PIPE-

There is a plethora of info at both CHARLOTTE and FERNCO sites.

Incidentally, each story pipe install should be supported by a clamp at each story level. Verify before cutting.

A pro needs to jump in and correct me if my method(s) suggested are not sound.

KULTULZ said:

Have you thought of just replacing those sections as needed in PVC/ABF? Additionally, PVC (use solid core as a minimum) will not contain sound as well as cast, something to think about while hosting a dinner party...

Click to expand...

I don't understand what you're asking? The plan is to replace ALL the Cast Iron with PVC starting at that hub just above the clean out in the photo I attached on page 1. Or, are you saying I shouldn't replace the Cast Iron with PVC at all? Replace only the the sections that tie into the Cast Iron stack?

I'm just trying to figure out the best method of transitioning to PVC from Cast. I think it will be the donut, but I have to figure out where I can order a range of sizes for the Cast Iron that I have, which is 4" (it says right on the pipe!). I will order $100 dollars worth of donuts, I don't care, just as long as one of them fits nice when I pull it apart.

As far as noises go, I can't see installing new cast iron in place of the old cast iron. Maybe I could insulate the stack with some Roxul or something?

Solid said:

I don't understand what you're asking? The plan is to replace ALL the Cast Iron with PVC starting at that hub just above the clean out in the photo I attached on page 1. Or, are you saying I shouldn't replace the Cast Iron with PVC at all? Replace only the the sections that tie into the Cast Iron stack?

I'm just trying to figure out the best method of transitioning to PVC from Cast. I think it will be the donut, but I have to figure out where I can order a range of sizes for the Cast Iron that I have, which is 4" (it says right on the pipe!). I will order $100 dollars worth of donuts, I don't care, just as long as one of them fits nice when I pull it apart.

As far as noises go, I can't see installing new cast iron in place of the old cast iron. Maybe I could insulate the stack with some Roxul or something?

Click to expand...

I am just wondering what the justification is in replacing all of the cast if just a few sections are bad. Personally, I am cheap. Just offering alternatives.

I think it will be the donut, but I have to figure out where I can order a range of sizes for the Cast Iron that I have

Click to expand...

FERGUSON. Go to their site and they should have the catalog(s) in .pdf

I will be quiet now...