Cast iron pipes are in thousands of homes across the United States because they are considered strong and durable.
While many disagree about the benefits and disadvantages to cast iron pipes, one thing is certain – using cast iron pipes to carry waste can lead to serious plumbing problems!
These pipes are more susceptible to rust and leaks than cast iron pipes used to carry water. If you see rust on the outside of your pipes – unless there is deep pitting – there isn’t usually a reason to worry. Underground waste lines very rarely fail because of external rust, usually the problem is out of sight, on the inside of the pipe.
The contents of waste lines can create hydrogen sulfide gases. When these gases oxidize, they produce sulfuric acid and the acid will corrode cast iron pipes.
You can expect to see two different kinds of cast iron pipe failure:
Problems at the Pipe Seams – Seams are created when pipes are formed during the casting process. In this case, the hydrogen sulfide gas has collected in the pipe and attacked a weakened seam.
Pinhole Cracks – These cracks are very small and will not be visible during an inspection. What you will see are blobs of rust under the horizontal sections of the pipe. These blobs can be very tiny or up to the size of walnuts. These rust blobs are often overlooked because there are no obvious leaks. As the leaks form, rust will expand over the pinholes and seal off the water.
When cast iron pipes are formed, they are “pit-casted”; this means the internal pipe walls are not all the same thickness. The thinner portions of the pipe wall will show the cracks and pinholes first, so be on the lookout for patches of rust in different areas of the pipes.
If you are ready to replace your old cast iron pipes, check out this blog post about how to remove cast iron pipes and install PVC ones.
image by kurisu