How do you join PVC pipe to old hub of cast iron fitting?


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Old 12-03-17, 03:37 PM
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How do you join PVC pipe to old hub of cast iron fitting?

First forum post here. HELP!

2" cast iron drain pipe connected to a bath tub totally rusted out. Looks like I have to use a sawzall to cut the old pipe off flush with the face of the fitting hub. (1) So do I simply get a neoprene reducer with those stainless steel bands to mate to replacement PVC pipe I'll run to the tub? Would it be worthwhile to lay down a heavy bead of silicone rubber around the butt joint of the PVC pipe and hub before sliding the reducer down over the outside diameter (green line) of the fitting hub?

Comments welcome.

NeutrinoBob
 
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Old 12-03-17, 03:49 PM
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I would probably get the oakum and lead out of the hub and use a compression donut similar to this one: Fernco 22U-205

But you would need to check and get the right size obviously.

Fitting inside the hub will catch less waste.
 
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Old 12-03-17, 04:23 PM
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How the joys of an older home.
Get rid of every inch of that old pipe including outside and replace with new PVC pipe!
If not your going to be playing wack a mole with pipe leaks.
 
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Old 12-04-17, 04:59 AM
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I know about wack-a-mole... But I'm on SSI... Digging out the 4" pipe will cost in the thousands since I can't handle it on my own. The run and minimal slope in the crawl space (more correctly slither space) is horrible with major duct work just inches off the ground covering up 8 feet + of the run. :
 
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Old 12-04-17, 05:00 AM
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I'm with Joe on this one. Replace as much of the cast iron as you can. In your case I would dig down and cut the female bell off the piece in the ground. That will leave you with pipe closer in size to the PVC and you can use a straight coupling. Use a rubber with a metal shield no hub coupling to join your new PVC to the old cast iron. Use NO caulk or sealers. That will make it easier to break the connection in the future when you have to replace the rest of the cast iron.
 
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Old 12-04-17, 05:09 AM
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OK thanks,
I've never dealt with cast iron pipe... So don't know how difficult it is to clean out the lead. With the probable fragility of the fitting, I'm not going to pound on it... Maybe I can drill-out the lead enough to gently pry out bits??? Then use the doughnut you suggest. It's not going to be any fun at all where it is located.
 
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Old 12-04-17, 07:36 AM
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Getting the lead out can be difficult. I usually just cut the pipe. A reciprocating saw and several sharp, fine tooth blades can do it. You can also use an abrasive cut off wheel though the noise and dust/smoke will be a problem in a crawl space. I would either cut above the fitting leaving about 4" of pipe protruding or get out the shovel and open up around the pipe in the ground and cut just below the bell. There are also cast iron pipe cutters you can rent or borrow that make quick work of it.
 
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Old 12-04-17, 07:47 AM
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Is there not even about 1-1/2" of usable cast iron pipe above the hub? That's all you need in order to install a shielded no-hub and you're in business.
That would be ideal because the no-hubs will not leak when installed properly.

If there is no usable pipe, then I agree the bell needs cut off. Cutting off the bell will allow you to use the proper sized no-hub.
No-hubs are a permanent fix so it's worth the effort. Silicone or other sealant will not fix any type of leak.
 
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Old 12-04-17, 02:47 PM
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No joy on saving a stub of the 2" iron pipe above the hub. Also I don't think there will be enough 'neck' below the hub to grab onto if I cut that off. Bought a cheap HF Sawzall knockoff this afternoon. Will go for the gold tomorrow and try to remember to report back with photos after my wounds heal. ;
 
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Old 12-04-17, 03:44 PM
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Get good blades for the saw will help and have several on hand as they will dull. When you notice the cut slowing down go ahead and put in a new blade.
 
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Old 12-04-17, 03:50 PM
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I would still use the donut, a lot less work. But if you are intent on cutting off the hub, when cutting cast iron with a metal blade, resist the urge to cut at high speed. Cut slowly, oil your blade frequently. Milwaukee torch blades are some of the best.
 
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Old 12-04-17, 05:45 PM
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Unless the hub itself is damaged I agree with X, let "sleeping dogs lie" is a better policy. Cut the existing cast iron an inch or two above the hub using an angle grinder with a cut-off abrasive disc. If it is as "tender" as you think it will likely be thin enough to easily break from the hub. Use a screwdriver or cold chisel to remove the lead and oakum and then a wire brush to clean the hub.

Install a rubber "donut" into the hub and then insert your new ABS or PVC DWV piping. A little dish washing detergent on the pipe as a lubricant helps when inserting the pipe. Alternately you could caulk the plastic into the hub using new oakum and then lead wool.
 
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Old 12-14-17, 10:14 AM
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Well here is my goof-ball solution for my particular delima. It works!

Maybe you will find this entertaining...Here was my dilemma… 2” Cast iron drain piping to a seldom used bathtub was found to have rusted out completely. Where? In the most inaccessible part of a crawl space, really slither space, under a 64 year old house. There is no space high enough to sit upright under the floor joists anywhere, much less where I needed to work. Inaccessible because duct work had been installed years later with total disregard for cutting off access to the plumbing. Well, there is access as long as you are willing to insert your torso in a 4 ft long tunnel under the duct work and between brick foundation piers. Clearance? About 2 inches off your chest while laying on your back and about 6 inches wider than my shoulders… When you get in as far as possible, my legs are still in the tunnel. Fun Eh?I decided to buy a cheap Sawzall clone so I could cut the rotted pipe off flush with the hub of the 4” sewer pipe buried in the ground. There appeared to be no possibility of cutting off the sewer pipe hub and then using a rubber reducer to mate up with 1 ½” PVC pipe. The other way would be to use a blowtorch to melt out the lead and dig out the oakum packing so that I could insert a rubber bushing. NO WAY in that severely restricted space was I going to fire-up a screaming hot high output blowtorch!At the local home center I could not find a stock way to make the transition from the cast iron hub to the PVC. Time to get creative and apply my shop capabilities to fabricate a durable transition to this non-pressurized piping application.I found they had a Fernco 3” rubber cap that has an i.d. of just about 3/8” less than the o.d. of my 4” sewer pipe hub. I thought that this rubber cap would stretch enough to fit. It was (with firm persuasion). I then thought I could mount a PVC fitting into a hole sawn in the cap. The fitting is a 1 ½” PVC MPT to Female Slip. My only problem was that I did not have a nut that would hold the MPT securely in the hole of my cap.My solution to that was to make a custom PVC nut out of a section of FPT thread in a PVC cap. Because pipe threads are tapered, I could not spin my homemade nut on far enough to tighten. The solution was to cut a slot in the nut so it could expand to the right diameter. To give the nut strength, I cut a groove around the nut and wrapped some stainless steel wire around in the groove… I only had enough for three wraps… As a safety measure I remembered that I have a big spool of 0.5 mm Kevlar braided cord (100 lb. test!) So I wrapped layers over the stainless steel and saturated the cord with CA adhesive. I DARE Father Time to cause my nut to fail in the next 50 years!Since I am a retired ‘belts and suspenders’ kind-of engineer, I thought it might be a good idea to try and make sure that the drain water never even gets in direct contact with my modified rubber cap. The opening in the remaining cast iron pipe is less than the o.d. of 1 ½” PVC pipe. Even a 1 ¼” PVC tail piece would not fit. What to do? I remembered that I had a stainless steel truck mud flap and I decided to cut off a strip that I could form into a flanged ferrule. This ferrule fits nicely down into the cut off iron pipe. The flange is flooded with the PVC cement so should never leak there. A crazy, but to my way of thinking, durable solution for this awful predicament. Robert
 
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