How to Replace Cast Iron Drain Pipe with PVC? [3 Easy Steps]

Cast iron pipes have a design that allows them to last for up to 80 to 100 years. While several variables determine how long a pipe lasts, the actual life can vary, which means that in some cases, cast iron pipes can fail before their predicted lifespan.

If your home is constructed around hundred years ago, your cast iron drain pipe life expectancy is around to expire, and soon you will begin to experience problems in your home. Older homes commonly have problems with the trees in their yards. Some pipes are derived from roots that run down the whole way to the water source. When trees are linked with pipes, they cannot coexist very well.

Pipes made of cast iron would need to be replaced at some stage. One of the most critical reasons why you should go for PVC is because of your household’s old iron pipes. Pipes made of iron are extremely large, requiring the help of many installation workers to lift and place one pipe. Due to their lightweight, PVC pipes are easy to lift and place, making it easy for the installer to handle the task. This minimizes the risk of accidents while also cutting down on costs such as shipping and installation. The pipes’ light weight helps in speedy installation.

Do you know how to replace cast iron drainpipe with PVC? Now, let us look and see what issues we can look out for.

Related: How to replace sewer pipe in the basement?

Table of Contents

  • Cast Iron vs PVC
  • How Do You Know Your Cast Iron Pipes Are in Bad Shape?
  • Can You Replace Cast Iron Pipe With PVC?
  • What You’ll Need
  • Replacing Cast Iron Drain Pipe with PVC (Step By Step Guide)
  • How Much Does It Cost to Replace Cast Iron with PVC Pipe?

Cast Iron vs PVC

  • PVC pipes are highly flexible, which means they’re less likely to fracture and less likely to leak or crack. PVC compound is unaffected by wear, and this results in its ability to resist breaking under pressure without fracturing. PVC pipes feature this unique feature, so they are commonly used in places that need pipes to resist high pressure and movement. PVC remains unchanged, even with pressures and vibrations applied. The thin-wall syndrome may occur in cast-iron pipes.

  • Iron pipes are susceptible to corrosion, which results in leaks, cracks, and the spread of germs and bacteria. The pipe replacement process is costly, but it must be performed every few years to keep the pipes from wearing out. There are no problems with PVC. The most advanced form of plastic that doesn’t crack, leak, or rust doesn’t have to be replaced after ten to twenty years, particularly if one pipe is used for multiple purposes. Since PVC is resistant to abrasion, it is an economical option.

  • Cast iron is a soft material. Water sloshing is a problem with PVC piping since water cascading down a vertical stack makes a lot of noise. It’s popularly thought that there is a leak behind a wall too noisy.

Related: How to Repair PVC Pipe in Tight Spaces? [7 Effective Ways]

How Do You Know Your Cast Iron Pipes Are in Bad Shape?

  1. 1

    Foul odor or discolored water
    Is there a foul smell of sewage or gas coming from your home? A broken pipe may be the cause of the noise. In addition, tap water that looks brownish or yellowish is the same as most tap water. Delivering water that has been discolored could mean your cast iron pipes are beginning to wear out. 

  2. 2

    Moldy walls

    Pipes that leak may also be indicated by mold on the walls. Mold won’t form unless there is a great deal of moisture present. Even a hairline crack in the pipe will lead to mold formation. 

  3. 3

    Sluggish drains

    When you flush a toilet or fill a sink, how quickly does the water drain? If your drains are slow, it may mean that your pipes have a problem. Caustic compounds are used to unclog blockages, and these aren’t suitable for cast iron pipes.

  4. 4

    A lawn that looks too good

    Have you got lush, verdant patches situated amidst a parched, ash-covered lawn? So, you might have a sewage pipe that is leaking. Finally, please note that sewage is harmful to humans, but plants can’t get enough of it. Keep your eye on any distinct patches of your grass, and track them. 

  5. 5

    Lawn or pavement indentations

    When the pipes are broken or leaking, puddles or pools of water from beneath your lawn or driveway. You can start to see some areas starting to sag and develop indentations if this lasts long enough. You should contact a plumber if you see anything that looks remotely like this. 

  6. 6


    It is important to be vigilant of any cracks in your base or walls. One of the many warning signs of a broken pipe is that it has remained uncorrected for a long time. If you’re not careful, sinkholes can grow. 

  7. 7

    Sewage Puddles

    Of course, you’d have to have a serious problem somewhere if you saw puddles of sewage on your house. Time is not anything to be wasted. Get in touch with a plumber right away. 

  8. 8

    Insect and Rodent Infestation

    If you think of cockroaches, flies, or rodents, damaged sewage pipes are probably not the first thing that comes to mind. While they may indicate that leak in your pipes somewhere, this does not necessarily mean that is the case. Please think of how simple it is for nasties (e.g., rats, cockroaches, and others) to crawl around even a tiny crack in your pipes. The issue may not be with the pest control company, so don’t keep calling them; it’s time to begin suspecting a problem with your pipes.

Can You Replace Cast Iron Pipe With PVC?

Pipes made of cast iron will last for years, but eventually, the pipes inside will rust. Caustic chemicals can speed up the process when used to open clogs. The removal of cast iron from residential sewer systems has necessitated a way to link new PVC pipes to the cast iron sewer system that is still in operation.

You will find a new PVC replacement pipe that is more sturdy and reliable than fix cracked cast iron drain pipe. Over the past few years, PVC has been the most widely adopted form of pipe due to the vast array of benefits, which is not possible with iron pipes.

Related: How to Connect PVC Pipe without Glue? [5 Methods]

What You’ll Need

  • Safety glasses
  • Chalk
  • Pipe supports
  • Reciprocating saw with special cast iron cutting blade
  • PVC pipe
  • Two rubber adapters

Replacing Cast Iron Drain Pipe with PVC (Step By Step Guide)

Step-1: Structural pipelining

A scant number of plumbing firms provide this approach, and it is not surprising. In addition, there may be financial and practical considerations for the property owner that overshadow the advantages. Which of these interests you? A serious issue is that cities don’t want it to be permanent. You can use this drain only in one part of the pipe; it cannot be used for the entire house.

The lack of drain capacity often creates problems with the building’s plumbing, which is not to code to begin with. New building code standards require property owners to replace the existing cast iron pipe diameters, which are smaller than the new code minimums.

In addition, the filler shrinks the pipe, which can make it worse in the future. An issue with the installation process is that the liner doesn’t make any turns. In this case, it also means the floor and walls must be opened to remove components and branches.

This may end up costing the plumber a great deal, as it takes less time to complete the job, and the property owner could end up paying less. However, this will not be a good idea for most people as a result is likely to be of poorer quality.

Step-2: Pipe bursting

When the host pipe, or the pipe it’s connected to, is made of a more fragile material, such as cast iron, we can use pipe bursting to replace it. Often known as a bursting head, this device uses a static or dynamic head to break apart existing pipes or compress them into the surrounding earth. Pipe bursting is the best way to cut cast iron drain pipe.

All these things are happening simultaneously: a new PVC pipe is mounted to the back of the bursting head and has the same orientation as the first.

Step-3: Spray lining or brush coating

Pipe coating or spray lining is done using a sprayed-on polymer resin. This is a type of trenchless pipelining. The lack of a structural liner composed of felt-like material, fiberglass, or other material is a critical difference between this approach and structural pipelining.

Epoxy resins have historically been mostly used for pipe coating, but pipe coating without a structural felt liner also leads to brittle epoxy and cracked pipes. Re-pipe’s proprietary polymer resin enables the same sewer rehabilitation advantages as epoxy spray lining and brings a layer of versatility never seen before. This machine is useful for repairing sewage pipes that are from 1.5 inches to 6 inches in diameter.

PVC pipelining and PVC spray lining effectively replace old cast iron pipes without the need to dig.

Related: Sanding Epoxy Resin [Complete Guide on How to Sand Epoxy Resin]

How Much Does It Cost to Replace Cast Iron with PVC Pipe?

The cost to replace cast iron drainpipe under house is between $200 and $15,000. This range depends on the project’s scale, the materials used, and the labor involved. A substantial amount of work must be done to cut into walls or flooring, which takes time.

You can buy a new PVC pipe in the range of $0.50 to $20 per linear foot. When calculating materials prices, plumbers typically increase the markup by 50% to 125%, creating a commodity price range of $0.75 to $30 per foot that does not include labor.

Final Words

When I think about it, I realize that the majority of cast iron systems should be replaced. Once we know the trigger, this will not be necessary for the future. Cast iron drain pipe repair also a wastage of money.

So you should try to replace an old cast iron pipe with a new piece of PVC pipe. I hope that by reading this content, you would the get benefit.

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