Replacing Existing Cast Iron Sewer Line with PVC- Part 3 of 3

Published by Millennial1 on May 25, 2007 - 4:07am

When you’re remodeling an older house, especially one with cast iron sewer lines, it may pay to replace the pipe with PVC as part of the remodeling project. It will be much less expensive and emotionally draining in the end.

Now that I had decided to replace the existing sewer lines with PVC (Option 1 and 3), I obtained several bids from plumbing contractors. The final work plan was as follows:

  1. Remove and replace the existing cast iron sewer line with PVC in the garage,
  2. Install a sewer line from under the side of the house to the sewer main,
  3. Cleaning out the existing sewer line that went under the kitchen and
  4. None of the work entailed demolishing the downstairs kitchen floor or the new driveway. It took about three days to complete the work.

How we did it and findings
Workers demolishing garage floorThe plumbing contractor pulled the necessary permits and started excavating the floor of the garage. Thanks to the video camera work, he knew almost exactly where the old sewer pipe was buried.

The first area to be excavated was on the left side of the garage. The S-shaped excavation is on the right side from the downstairs kitchen

To our surprise, when the sewer pipe was removed, no breaks were found. However, we knew that we had done the right thing.

Excavation of sewer pipe from kitchen to garageThe sewer pipe was badly corroded and full of garbage that even a high power spray had failed to remove. The remaining piece of cast iron sewer pipe was not accessible. However, we used a rotary tool and some good flushes to clean it out. The flow was greatly improved.

Within a day, the plumbing contractor removed the entire sewer pipe under the garage. He also dug a trench from outside the wall and the inside and outside trenches joined under the footing. We contacted Miss Utility to mark all underground services on the property prior to beginning any excavation work outside.

The next day, with the help of tap drawings supplied by the county, the plumbing contractor excavated nine feet down to locate the sewer main. At the same time, he attached new PVC pipe to the remaining cast iron under the kitchen floor and laid to the outside of the house.

Clean outs being installedAt this point, the contractor installed two clean outs – one facing the house and the other facing the sewer main. The plumbing contractor explained that this would allow cleaning out of the new sewer pipe without having to enter the house.

The connection to the sewer main was most interesting. The main was concrete, approximately 18 inches in diameter.

The contractor also had inserted a test tee in the run leading from the house. Using a plug, the contractor filled the pipe with water from all the sink, tubs, and toilets in the house and left the pipe full of water overnight.

The next day, the county inspector came to our home. He checked for leaks along the sewer pipe's full length and, after releasing the plug in the test tee, leaks around the saddle. Everything checked out ok. Trenches were backfilled, cement floors patched, and landscaping redone.

What had appeared to be a major problem that could take weeks actually turned out to be a three-day project that worked out well – thanks to a knowledgeable plumbing contractor and the County's cooperation.

In hindsight, however, there is one lesson to share – when you’re renovating an older house, especially one with cast iron sewers, it may pay to replace the pipe with PVC as part of the renovation. It will preclude future problems that might require you to relocate for some time and, if done in concert with other contracted renovation work, work out much less expensive and emotionally draining in the end.


If you don't mind sharing, what was your total cost? I have a similar issue and am just starting to figure out what my options are. Great pics and thanks for sharing. Very interested stuff.

Hi rdobs
Sewer line repair cost approximately $5,000. Can't recall if that included the scoping now. Get at least three bids and get references. We were fortunate to have a great plumber but he passed away this year. May he RIP.

Also is the problem in your house or outside of the house. That may determine who's responsible. Call the county if you have not done so already, they may take a look at it with a scope free of charge.


The problem is with plumbing that runs under our basement floor. One side of the house services the washer and kitchen sink. This leg of the drain system goes under the concrete basement floor and meets up with the other drain that services two bathrooms with showers.

The side with the kitchen and laundry seems to have continuous issues and a drain in the basement floor consistenly overflows. We have had several plumbers out to clear it and take extreme care in the size of laundry loads and what goes down the kitchen sink. Same issue. It appears the size of the pipes or some other issue with how this drain connects to the main drain has an issue.

We haven't had it scoped yet, the plumbers we had seemed mystified when I asked them about this.

Very strange that the plumbers in your area are mystified about scoping the sewer line. It's fairly common here in the Washington DC area. Many plumbers don't have scopes, the larger companies do.

Scoping the sewer line will literally shed light on what the problem is and where it is in your case. Could be a clog, a tree root, etc. Might even be the part of the plumbing you think is ok.

Take your time and get things scoped especially before tearing up the basement. In our case the scoping localized the problem to the garage area and we didn't have to dig up our basement kitchen....thank God. It really provided information on the overall scope of the problem and in your case will do the same thing. You'll be able to see the problem. We also scoped it right to the country sewer so we could make sure that the problem was not on their end.

The alternative without the scoping is to tear things up and "hope" you identity the problem and correct it. Not a good idea in our opinion. Let us know how it worked out.


I have been charged roughly $800.00 per concrete beam 4 supposedly were installed. Is this a normal price for such an item. I live in San Antonio, Texas. Please give me your advice. I feel that I am been scammed. I am 80 years of age and suddenly find my house with enormous holes under a very steady concret foundation. All that was necessary was the replacement of cast iron pipes with PVC Pipes. The cost so far is $24,000 and climbing. I just do not understand why it is taking so long and so costly. Please help me.