cast iron pipe repair of joint

Repair a Cast Iron Pipe Joint in 3 Steps (Way Easier Than You Think!)

ByDino Pelle

Have you stayed away from making a cast iron pipe repair because you think it’s far too difficult? If so, then this article is for you.

I’m going to show you — in just 3 steps — how to repair a cast-iron pipe’s joint, the most common area for leaks and corrosion.

Cast Iron Pipe Repair: Instructions

Old cast iron pipes are intimidating for homeowners. Because they lasted so long without problems, most people ignore them. But you do so at your own peril. All cast-iron pipes eventually break, corrode, or leak. And when they do, it’s often a leak from the cast-iron joint.

Most cast-iron drainpipe is connected at bell-shaped hub-and-spigot joints, which are sealed with molten lead and rope-like material called oakum. If water leaks from such a joint, this is what you’ll need to do.

1. Service Lead-Caulked Joints

  • Use a hammer and cold chisel to tamp down the lead inside the hub.
  • If this doesn’t work, measure a length of oakum twice the circumference of the pipe and pack it evenly inside the hub with the end of a caulking tool or old screwdriver.
cast iron pipe repair of joint - step 1
Since lead is soft enough to be reshaped over the weak spot, this simple procedure should reseal the joint.

2. Prepare the New Caulking

  • Cold caulking compound and “plastic lead” have replaced molten lead as a caulcking for cast-iron joints.
  • Measure a length of the rope-like caulking compound twice the circumference of the pipe and cut it with a sharp utility knife.
  • Place the length on a clean, dry surface and dampen it (but do not soak it!) with water. Use a clean paint brush or a plant sprayer.
cast iron pipe repair of joint - step 2

3. Tamp the Joint

  • Work the dampened compound into the joint a few inches at a time.
  • Then tamp it down with a hammer and caulking iron.
  • Continue adding and tamping the caulking a few inches at a time until the complete length has been packed into the joint.
  • Wait at least six hours for the compound to harden before using the drainpipe (it’s best to leave the house for that amount of time to make sure no one uses the toilet, etc.).
  • If you use “plastic lead” (an alternative caulking material), it should be mided with water and troweled into the joint with a putty knife or old screwdriver. After you’re done, just like in the previous step, wait six hours before using.
cast iron pipe repair of joint - step 3
The key in this final step is to gently but firmly press the dampened compound into the joint. Don’t hurry this process or you will destroy your cold caulking compound.

Final Thoughts

Those old cast-iron pipes, most often found in older homes, look intimidating. That, and because they lasted so long without problems, is probably why homeowners are often too scared to mess with them. But they eventually break, corrode, or leak. And often it’s from the cast-iron joint.

Call 1-Tom-Plumber

Don’t hesitate to contact us here or call us at 1-Tom-Plumber (1-866-758-6237) if you need help with a drain repair or replacement, including your stacks and vents.

1-Tom-Plumber’s certified team of plumbers and drain technicians respond immediately to any emergency plumbing, drain cleaning, or water damage problem. We also handle the excavation of underground water lines and sewer main lines. Our immediate-response team is available every day and night of the year, even on holidays.

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