Cast Iron Sneaking Up

Posted on Friday, December 6th, 2013 by Nathan Weinstock

The plumbing system in a typical Ottawa rusty-drain-s-168x300home has two parts. There’s the supply piping that brings fresh water in. Then the drain-waste-vent (DWV) piping system, usually referred to simply as the drains, removes the ‘used’ water.  During a home inspection, it would be glaringly obvious if there was a serious problem with the supply piping. Water would be spraying all over or pouring into the house.

Problems with drain piping may not be quite so apparent. There could be rust and decay lurking inside the pipes that you would not know about until they fell apart and started to leak. Your household drains can be made of plastic, copper, galvanized steel, cast iron, brass/bronze, and even lead.

Let’s talk about cast iron as an example.  It was extensively used up until the 1960’s and presents its own unique set of problems. Iron, as you may know, can oxidize. That means it rusts. This is done in the presence of water and air. Where do you get this combination with a cast iron pipe? The answer, on the inside. So the deterioration, the rusting, happens slowly, silently, and out of sight, inside the pipe.

Cast iron failure generally occurs precipitously (suddenly). The pipe will work fine and reliably for many decades, and then, it will disintegrate right before your eyes. Just a light tap or hit can cause major disintegration or rupture.

Sometimes, if you are lucky and are paying attention, you get some warning, like rusting and staining on the outside (see the picture).

So, if you have drains made of cast iron, and they are over 30 years old, you should pay careful attention to them. Watch them closely so can you catch any deterioration or leak early on. Or better yet, replace them with new plastic piping. This is fairly easy to do and not that costly. That way you don’t have to worry about damaging drain leaks sneaking up on you.