How Long Do Cast Iron Pipes Last?

I've been looking at different properties to buy, and some have cast iron pipe plumbing. So, I was curious about how long do cast iron pipes last.

I did some research, and here's what I found:

As a general rule, cast iron pipes will last around 80 to 100 years. The leading cause of replacement of cast iron piping is leaking from the joints which are difficult to repair. Most plumbers opt to replace leaky sections of cast iron piping for PVC piping which is lightweight and easier to work with.

Plastic pipes such as PEX and PVC are relatively new, so it's unclear exactly how long they last, but the general consensus is that they last around 50 years.

Below, I will explain whether you should buy a house with cast iron pipes, how to know if you have cast iron pipes, and how much it costs to replace cast iron pipes with PVC.

Should I Buy a House With Cast Iron Pipes?

When you're looking to buy a house, you want to be aware of any additional costs like repairs that will need to be done to avoid any surprises in the future. So then, does it make sense to buy a house with cast iron pipes?

Overall, it is perfectly fine to buy a house with cast iron pipes. Regardless of what plumbing a house has, be it cast iron, copper, or PVC the plumbing is susceptible to suddenly needing to be replaced.

It's highly recommended to have the plumbing inspected prior to buying a house.

There are a few different options for getting the cast iron plumbing inspected, which are:

  • A sewer scope
  • A building inspection
  • A plumbers assessment

A sewer scope is where a thin camera is threaded through the lines to look for any issues. And as part of a building inspection, they will inspect all the pipes on the house, which will include identifying any leaks.

A plumber can also inspect the pipes to see how long they think the cast iron pipes will last. The cost to replace cast iron pipes can be in the 10's of thousands of dollars. Therefore, it can be worth it to spend some money to make sure the plumbing is sound.

At the end of the day, it's up to you how much risk you want to take on the plumbing. Certain aspects of it can also be covered by insurance, so it can be worthwhile working with the seller where possible to ensure the plumbing is in good condition.

If plumbing issues are found during the home inspection, the price of the home can also be reduced.

It's also possible to visually inspect the cast iron plumbing yourself. Here are some easily identifiable signs that cast iron plumbing needs to be replaced or repaired.

How Do I Know If My Cast Iron Pipes Are Bad?

The major signs that indicate cast iron pipes inside the house are already in bad condition are:

  • Water discoloration
  • Leaks
  • Poor water pressure

Cast iron is also used in the sewage lines that go from houses to the main lines. There are also some telltale signs that the cast iron pipes leading out from the house need to be replaced. They are:

  • Ground sagging
  • Slow drainage
  • Pooling of waste water
  • Areas of the yard that are growing better than others

I'll provide a brief description of what they look like and why they indicate that the cast iron plumbing may need to be replaced or repaired below.

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Water discoloration

If the water that comes out of the tap is not perfectly clear, it's typically because there is a blockage in the lines. The inside of a cast iron pipe can slightly rust, which creates a rough surface. 

The rough surface catches tiny particles in the water and causes a build-up. Some of the build-ups can break off and be suspended in the water, giving it a funny color. Also, if it's partially blocked with rust, part of the rust will wash off into the water and give it an orange tint.

Leaks in Cast Iron Piping

Easy-to-spot pools of water underneath the pipes are an obvious indication. You may also see droplets of water forming at certain points along the pipes. These usually need to be repaired very soon as they can rot the wood. It's harder for them to dry in colder months, leading to a bigger and bigger puddle of water.

Ground Saggage

If areas of the ground surrounding the house are lower than other areas, it could indicate that the pipes leading out from the house have a leak or have burst. The excess water can cause the ground to sag. It's also perfectly natural for the ground to sag in certain places. So, to know for sure, you'd need to do a sewer scope.

Slow Drainage in Cast Iron Pipes

When the pipes are clogged leading away from the house, the water will take longer to go down the drain. You'll notice the sinks don't drain at the normal speed, and you might get pools of water on the exterior of the house near the drains.

Pooling of Waste Water

When there is a rupture or leak, wastewater can create small puddles in the yard and be wet even when the rest of the yard is dry, and it hasn't rained recently.

Areas of the Yard That Are Growing Better Than Others 

Sewage is natural compost for the garden, so when there's a leak or rupture in the pipes leading away from your house, it can have a positive effect on the plants in your yard. It's very identifiable if there's also a foul smell to the area that's growing better than others.

How Do You Identify Cast Iron Pipes?

Pipes all look quite similar, so how can you tell if the plumbing you have is cast iron?

Cast iron pipes typically have a dull black finish. They also have unique bumps on each of the joins that aren't present in PVC pipes. When you tap on them, they should also produce a dull metallic sound. Copper pipes also have joints similar to cast iron, but copper pipes have a distinctive orange/red color.

If you're unsure whether they're cast iron or not, it's best to take some photos and post them where you can ask for people's opinions.

If all else fails, you can get a plumber in to take a look at them. But, they'll likely be happy to tell you free of charge or at a low cost if you send them photos of the pipes.

How Much Does It Cost to Replace Cast Iron Pipes?

Cast iron pipes are heavier than PEX and PVC and therefore are more difficult to remove when they need to be replaced. But, how much does it cost to replace cast iron pipes?

In total, it will cost roughly $10,000 to $20,000 to replace all cast iron plumbing with PVC pipes. Repairs to small sections of cast iron piping can range from $300 to $1000. Repairs of cast iron piping typically involve replacing cast iron with PVC.

Certain cast iron plumbing systems can be more or less expensive to replace, depending on how difficult it is to access the pipes and how large the house is. Also, certain states, cities, and towns are more expensive than others due to having higher average incomes and prices of materials.

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Hubert Miles

I've been conducting home inspections for 17 years. I'm a licensed Home Inspector, Certified Master Inspector (CMI), and FHA 203k Consultant. I started HomeInspectionInsider.com to help people better understand the home inspection process and answer questions about homeownership and home maintenance.

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