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Prepare Pipe Ends and Install Couplings — Install the Shielded Flexible Coupling

Beginner6 hours

Part of project

How to Connect a PVC Drain to a Cast Iron Pipe · Step 7 of 9

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In this video

After removing the old pipe, the plumber prepares the remaining cast iron stack for the new fittings. He uses a strip of emery cloth to sand and clean the cut ends of the cast iron, removing any rust and burrs to ensure a smooth surface for a proper seal. He then slides two 3-inch Fernco flexible couplings onto the cast iron pipes, one on the top section and one on the bottom, pushing them out of the way to allow for the installation of the new PVC section.

Goal: Plumbing Pipes Repair

  • A clean, smooth surface on the old pipe is essential for achieving a watertight seal with the new flexible couplings.

Used in this video

  • Emery Cloth (Tool Type: Hand Tools, Abrasiveness: Medium)Sanding and cleaning the cut ends of the cast iron pipe.
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Roger Wakefield Plumbing Education

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FAQs

What are the most important safety precautions when cutting cast iron pipe?

When cutting cast iron, always wear 3M Professional Chemical Splash/Impact Safety Goggles, MCR Safety BearKat Safety Glasses, and a 3M P100 Household Respirator to protect against dust and debris. Cast iron is heavy, so ensure the pipe is well-supported with 2 in. x 4 in. dimensional lumber before and during cutting to prevent injury or damage.

Do I need a special blade for cutting cast iron with a reciprocating saw?

Yes, a standard reciprocating saw blade will not work effectively on cast iron. You will need a Milwaukee 12 Amp SAWZALL Reciprocating Saw equipped with a DIABLO 9 in. Diamond Grit Reciprocating Saw Blade for Cast Iron Cutting. This specialized blade is designed to cut through the hard material efficiently and safely.

How do I properly support the cast iron pipe to prevent it from falling after I cut it?

Before making your cut, use 2 in. x 4 in. dimensional lumber to create temporary supports on both sides of the cut line. Secure these supports to a stable surface, ensuring they can bear the pipe's weight and prevent any movement, cracking, or collapse during the cutting process.

Why is a shielded flexible coupling recommended for connecting PVC to cast iron, and how do I install it correctly?

A shielded flexible coupling creates a durable, leak-free seal between cast iron and PVC, accommodating slight differences in pipe diameter and vibration. Ensure both pipe ends are clean and deburred before installing the coupling, then tighten the stainless steel bands evenly to the manufacturer's specified torque using a TEKTON 7/16 in. Nut Driver.

Transcript
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all right let's start putting this thing back together let's just connect this trap from the laboratory one on the other side of the wall for just working all right let's take a moment and review before we decide to put everything together I'd say we got pretty darn lucky on that man all the odds were up against us we had that live gas line sat right there all the water lines wrapped around the drains not to mention the stacked and drop on us I mean you can't just come into these jobs and think that everything is going to end up perfect you got to exercise some serious precautions if not you're going to be in an emergency really fast and this is not the kind of house that I want to end up flooding out it's rental and they're small children and babies inside of here that's why there's so much noise and get something to drink we'll head back in and see how we can put this all back together we're going to start with two three inch front hose slip one there we're going to slip the other one up here and just kind of snug it for the time of year

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