Replace Cast Iron With PVC
Replace Cast Iron with PVC TIPS
- Only replace cast iron if cracked
- Cast iron is not noisy like PVC
- Use stainless-steel hub adapters on cast iron
- Watch my PVC VIDEOS Below!
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Tim the Master Plumber
Before we go any further, you need to know I'm a master plumber as well as a builder.
I got my master's certification back when I was about 29 years old. I've always loved to install plumbing as well as threaded black iron pipe. I cut my teeth doing many a remodeling job where I had to crack into a cast-iron drain stack and plumb in a new branch line for a bathroom or kitchen remodel job.
I discovered in no time that cast iron drain piping was durable, it was soundproof and it lasted for decades.
What's more, modern cast iron pipe is made differently than the old cast pipe. A hundred years ago they actually had molds they poured the molten iron into to make the pipe. These molds could have places where the side walls of the pipe were thinner than other spots. These thin sections could rust away.
Modern cast-iron pipe is made by spinning the metal and the pipe wall thickness is uniform.
Cast Iron vs PVC
If I were building a new home today, all of my drain lines would be modern cast iron. All my vent lines would be PVC. Watch my plumbing vent line video below to see this complex system of pipes that exists in the walls and ceilings of your home!
Plumbing Vent Video
PVC pipe is noisy. If a person flushes a toilet and the drain stack is not wrapped with sound insulation, you'll hear the water crashing against the sides of the pipe as it goes down the wall.
You'd think there's a waterfall inside your home it's so loud. You never hear this if you use cast iron.
Lanny, who lives in Campbellsville, KY, asked me a great question about old cast iron drain pipe.
"I'm going to renovate my bathroom and my main drain line for the water and sewer is the old black cast iron pipe. Is it against the code to keep the cast iron pipe or do I have to replace it with the PVC pipe?"
My Answer - You Already Know What I'll Say
Well Lanny, since it's impossible for me to memorize all the different plumbing codes across the USA, I can't tell you what the inspectors in your city would require. While there's a model plumbing code baked into the building code, cities and towns can and do modify it to their own local practices.
But here's the bottom line. Cast iron is a wonderful material. If I was building a new home today, and I plan on doing one in the next few years, it will have cast iron drain lines.
Cast iron is quiet. The issue with PVC is that when water cascades down a vertical stack it sloshes around and it's very noisy. Some who hear it think there's an actual leak inside a wall it's so loud.
It can last for hundreds of years. It's the most durable interior drain pipe you can install.
Newer cast iron pipe is made so the wall thickness is uniform. Old true cast iron pipe could suffer from thin-wall syndrome, but that's no longer an issue.
It's also easy to work with if you're creating a new branch line. You can use stainless-steel no-hub clamps to make leak-proof connections in case you want to run PVC into the cast iron.
I vote that you keep the cast iron and add new branches as needed. You can add new cast iron to old as well as blend PVC into the system if you want.
I want to add that my vent system in my new house will be PVC. But any drain line that handles water and waste flow will be cast iron.