How can I seal a cast iron pipe besides trying to weld it?

dronic123 · February 8

I have a vertical cast iron drain pipe which is cracked for a substantial length-perhaps 3-4 ft. Perhaps it froze?
Anyway, is there a way of sealing it up. I don’t think you could weld it andit looks like it would be difficult to braise. Is there some sort of mechanical joint type fitting I could use? Could I just paste it in epoxy?

delcrossv · February 8

Cut it out with a carbide sawzall blade and put in a piece of no hub CI with a couple of "fernco" couplings.

See:

https://forum.heatinghelp.com/discussion/185090/weird-cast-iron-failure

Jamie Hall · February 8

A drain? Shouldn't ever be under any pressure to speak of, so I would clean it up really well — wire brush at least, maybe even a light grind. Then use JB Weld on it.

EBEBRATT-Ed · February 8

The JB weld may work for now. The right fix is to buy a new piece of pipe. Cut out the damaged piece. You can cut it with a sawzall but it will take a while, and you will go through some blades.

A 4" angle grinder with a cutting disk will cut it like butter. I would not use a pipe snapper if you have cracks.

Make sure to ware safety glasses and gloves when cutting. Cut the new pipe about 1/2" shorter than the old piece and connect it with 2 no hub couplings.

Make sure to support the upper pipe with hangers or a riser clamp so it doesn't settle

You can't weld it. You could braze it but I would not.

hot_rod · February 8

it is tar coated, so any type if weld or braze would be stinky and a fire hazard

A carbide sawzall blade would remove it quickly any reason it could not be pvc or abs ?

Mad Dog_2 · February 8

If you're gonna use a Sawzall..ya gotta use a Diablo blade. I'm very skeptical by nature & don't run to join the latest trend, but Diablo is so much faster than Milwaukee or Lennox blades. Mad Dog

mikedo · February 8

plastic seal caulk its made to seal cast iron drain pipes but eventually it will have to be replaced

kcopp · February 8

A temp Fix is Hercules Plastic seal. Comes in a caulking tube.

25215 - Hercules 25215 - Plastic Seal - 10.3 oz.

Intplm. · February 8

Pretty much everything said above is good. If you do not have the means to cut it free to replace the pipe get your self a stick of two of this stuff. It works wonders with no drips. You mix it like play-do and push it into the crack. It will harden, making a strong repair. Works every time.

Jamie Hall · February 8

As noted there are a number of epoxy or other compounds which will do the job.

However.

None of them will work for beans unless you thoroughly clean where they are going to be put. And I do mean thoroughly.

Long Beach Ed · February 8

The two part epoxy that Intplm and kcopp recommend works well for a few years, if you clean the surface with a grinding wheel first. Eventually the rusting crack pries the pipe open. There are fiberglass "casts" that are wet and wrap around the pipe that work very well. A plaster cast will work too, and is permitted in the NYC code (if the inspector doesn't laugh at you). None are permanent, as rust will always win and the pipe will continue to crack and leak again.

MadDog is right about the Diablo blade in a Sawzall. Cut out the bad section and replace it with new cast iron or PVC piping using no-hub (or Fernco if permitted) couplings. Then you're done.

Ironman · February 8

If the pipe has a linear crack, epoxy or JB weld won’t stop it from cracking further.

The best thing is to cut it out past the crack and replace it using Fernco couplings as suggested.

SlamDunk · February 8

I had a 4" cast vent with a linear crack. Jb weld, with a Flex Seal chaser.

psb75 · February 9

In metal work isn't it standard practice to drill a small hole at both ends of the crack to stop it from "running further" before brazing/welding/epoxying?

dronic123 · February 9

thanks everyone

I was hoping there was some sort of rubber patch/super duct tape / flex seal that would go over the crack and then some sort of wood strip and gear clamp to hold it all in place. Anyone ever use flex seal spray?

Yes the easy answer is to cut it out and replace it. Question- if you replace the 4” cast with plastic-will the fernco couplings work?

@ Long Beach Ed : Is plaster cast just “plaster”?
Can you further detail the fibreglass patches—perhaps epoxy covered cloth might work better given the water issue?

Larry Weingarten · February 9

Hi, I have cut out vertical split cast iron pipe and used Fernco type fittings and ABS pipe (I'm in the West where we use ABS) to fix it. The one thing to bear in mind is that the pipe above may sag down when it loses support, so be prepared for that and have the pipe restrained somehow.

To use the Fernco fittings, I slide the stainless cover up (or down) the pipe, then push on the rubber piece. Then roll the rubber up over itself to leave room for the new pipe. After the new pipe is in place, roll the rubber over it and then slide the stainless cover into place and tighten things up. Of course, you get to do these steps together at both ends. I'll add that I'd want to use the type of Fernco that has a metal cover over all of the rubber, to help hold things straight together. I would avoid the rubber type that simply has two hose clamps.

Yours, Larry

Long Beach Ed · February 9

Fiberglass pipe wrap. They come in different width and lengths. They work for maybe five years at least:

https://www.amazon.com/FERNCO-FPW248CS-Pipe-Repair-Kit/dp/B000JD6JVC/ref=sr_1_6?crid=JTRTYNQXJF0B&dib=eyJ2IjoiMSJ9.u22nk0wGdTDdbnrAgv9Nnaf40JWmR4BJ_mfbO8KvUYCG-zCjKPjfQF3XlbKImdiHhg_zYXrAeyuafQ8Yk9BbWwzhsnM6r-Xo23H7b0qAewt6yigM9AMngZ9rEtV0_geFcPXtH6dra_7UeVuidi6JVO4EPb47PbL79naBwnV-6x4eH7re_vXX4Z1_aCavl9qn72-RmNz-idTRUeMc6L3KApVh0heYqFLipmMgL4jqoNc.wrowS_qrXd3zTZpk8kpDRcafht-pi5-mntyy3zo4e3c&dib_tag=se&keywords=pipe+patch&qid=1739112352&sprefix=pipe+patch%2Caps%2C280&sr=8-6

DCContrarian · February 10

I'm old enough that five years doesn't sound very long and not old enough that it's long enough.

dronic123 · February 19

@SlamDunk : thanks for your comment—-did you use the flex seal spray?/or liquid? did you have a pipe with a tar or coal tar surface—if so did the flex seal stick and dry up satisfactorily? how long has it worked (without re-leaking)? did the flex seal stick satisfactorily to the jbweld?

SlamDunk · February 20

@dronic123 I used spay on top of jbweld to reach areas in a wall that I couldnt reach by hand. The jb weld is doing the lion's share of the sealing and the flex seal captures hair line cracks. It has worked for a year so far. There also was an abandoned tr arm that I pulled down and filled with epoxy and sprayed. Here is a before pic:

jumper · February 20

Long long ago you could buy tape to patch your car's muffler. Heat activated some stuff in it. It would work for a week or two. Wouldn't it work on a drain pipe indefinitely? Maybe the correct caulk will as well. One method to clean cracks is to fill it with sticky caulk and then remove that caulk.

How can I seal a cast iron pipe besides trying to weld it?

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