Home Improvement Ideas Plumbing Installations & Repairs How to Repair a Cast Iron Pipe Learn how to repair small crumbles or leaks in an old cast iron pipe with our expert-backed advice. By Caitlin Sole Caitlin Sole Instagram Caitlin Sole is the senior home editor at BHG. She is a writer and editor with nearly a decade of interior design expertise. She has vast experience with digital media, including SEO, photo shoot production, video production, eCommerce content, print collaboration, and custom sales content. Learn about BHG's Editorial Process Updated on July 24, 2022 Share Tweet Pin Email Old cast iron drainpipes can behave unpredictably. Sometimes a small section of a pipe starts to crumble or a joint begins to leak even though most of the pipe is sound. If this is the case in your home, you can—in most cases—easily make the repair yourself. However, if a cast iron pipe fails at several points, the most economical solution is to replace it with PVC pipe, which is a job for a professional. Cast iron pipes are very heavy and must be held in place with special clamps and framing members. When doing repair work on a cast iron pipe, it's important not to disturb these clamps—if one weakens, a long section of pipe could come crashing down. In addition, some older cast iron joints were sealed with molten lead, but this does not pose a danger to your health because only wastewater passes through the pipes. If you need to patch a joint on a cast iron pipe, expect to spend an hour or more doing so. If you're just patching a hole, it may take even less time. What You Need Wire brushHammerCold chiselPutty knifeRepair paste or plumber's epoxy Step 1: Clean Away Corrosion If you spot water or a bad smell coming from an old leaded joint, use a cold chisel and hammer to gently tap the lead back into the joint. Use a wire brush and rag to clean away any corrosion. Step 2: Fill with Repair Paste Fill the resulting void with cast iron pipe repair paste, using a putty knife to apply the paste evenly. Step 3: Fill Any Holes If a pipe rusts through or is punctured, clean the opening with a wire brush and fill the hole with a two-part plumber's epoxy. Check the manufacturer's instructions for drying time, and make sure the pipe isn't in use until the patch has been completely set. Was this page helpful? Thanks for your feedback! Tell us why! Other Submit