How long it can take a cast iron to disappear from a thick drain pipe because of rust?

Hi JB...

It all depends on the chemicals used in a home over time. It can take years, even decades for a cast iron pipe to rust through.

Why do you ask?

Mark

Hello Dear...
First of all Thank you very much for your prompt and a true professional comments.

Why I asked this question?

It is a long story.. It is related with Heating Water Pipe leak investigation was going on in my home under my Home Insurance Cover. In first stage everybody who were investigating the leak point's location, were focusing to locate Hot water pipe leak. But when the floor of the kitchen was opened to see the pipe , what we see that there ia at least 20 cm "Balck Water" standing on the ground . Insurance hired company called "water sucking car" to suck the water out.
The man came and started process of sucking water thinking that they are sucking water which has been caused by Hot Water pipe leak... but all sudden the man noticed a Condom floating on the water... His immediate reaction came by saying that this leak is not because of Hot water pipe but also some Sewer Pipe has been leaking...
Any way they did their job and left, but could not see the leak point anywhere..
Last week a bigger whole was made on the kitchen floor so that we can access easily under the ground and see and locate the damage pipe..
Ultimately what we found... The sewerage pipe has been damaged. 70 cm in length... and 75% of the cast iron metal has been eaten by the rust from the upper portion of the pipe. Rest 25 % down portion is still attached and water is flowing out of that part .

Now the main issue is Insurance Company.

I had insurance of the house continuously ever since I bought this house in 1997. But because of my divorce I had to leave my home to my ex wife during 2-2006 to 2-2008. My home was without insurgence cover from 23.03.2007 to 17.01.2010.

Now when insurance need to cover this leakage loss caused by sewerage pipe... they want to establish that this accident happened during that period when there was no insurance of the home. It means during 23.03.2007 to 17-01-2010.

So my question is this can it be possible a thick cast iron pipe can be eaten by rust (75%) during 3 years since it started leaking.

It will be a great help for me to know your own professional judgment in this case.

I will appreciate your answer if possible soon.

Jatinder Last Name Removed by speedball1

Hello Dear Mark,
Here I have translated the report from Finnish to English, written by inspector hired by insurance company.

ADDENDUM TO REPORT 10.09.2010:
The kitchen floor of the inspection opening is enlarged when observed in the shower room floor
Crawl space of the cast-iron sewer pipe is corroded at the top of punctured approximately 0.7 m length.
Spilled sewage pipe could not be detected without opening the kitchen floor. Sewage outlet pipe has drained
Water on the bottom probably for several years, crawl space moisture is caused by
Heating pipe corrosion and leakage. Heating pipes have many small
Holes in the kitchen floor of a hole in the case of the heating tubes the outer surface of the rust
Kitchen and laundry room wet bar on the base floor interval case. The base floor of the crawl space
Muottilaudoitus ( wooden structure) screed has been damaged because the planking has been in moist air, and the uprights at their lower end
Have been in the water.
Technical state of the concrete floor is opened inspection hole, found that the base floor crawl space bottom
On the water. Water is also a sauna room below the floor.
Proposal given is to open the laundry room and sauna floors to laundry room, sauna and technical space
Below the sewer lines may be renewed, floors muottilaudoitus ( wooden structure) to be removed, the base floor bottom
Decontamination of sewage sludge and disinfection. Kitchen floor needs to be unzipped wet bar spacing
Split (outside the wall), then muottilaudoituksen floor landing, the base floor bottom
Cleaning and disinfection. Heating pipes of a new kitchen, laundry room and technical space
Elastic. Also, the washing room, kitchen, sauna, and technical status of the base floor of the new water pipes would be
Recommended. The living room floor of a manhole Making toilet against the wall in order to
Ensure that the sauna has reached below the water in the base floor living room. WC base floor
Verification of the sauna floor after landing. Utility room floor because the floor under the opening of the
Got water in the shower room wall below the bottom of the grip.
Base floor got wet surface drying Piku 2

My opinion on the cast iron pipe is that cast iron breaks down over decades... not just within a few years.

Since the pipe was under the floor there is simply no way to determine when the corrosion broke through the pipe, but I am sure it has been breaking down/thinning out for a long time.

How big is the pipe in question and has anyone discussed RELINING the pipes instead of chipping/digging out the floor and replacing the pipes?

Relining will typically save thousands compared to completely replacing the underground pipes.

Read what Tom has to say about relining pipes below.

Let us know if you'd like to discuss... OK?

Let me explain a bit more about my drainage problem and how I repaired it. 54 year old house. The builder used sub standard cast iron in the drainage. The 4" house main was completely ate up on the bottom of the pipe , blocked with roots and welling up in my living room floor. I was sure that the main had broke in two and I would have to jack hammer up the floor and tunnel under the foundation to transition to PVC, pick up the back bath and move the main outside the house but I had to know what was going on under the slab so a friend suggested running a camera down there. There was no distinct break in the main, however,it was completely ate up on the bottom. That's when Rooter Man of Sarasota and Gulf Coast Florida suggested relining the main, (see image). It took a day to clear the roots and pressure jet clean the main. Next day they came back and relined the main with epoxy. I now have a sewer main that will out last me, (50 year guarantee) and the best part is that I didn't have to, tear up my house and the cost was under half of what I figured to take the main outside around the house. Another bonus was that it was done without tearing up or disturbing my house. When they were finished I kept a piece of the epoxy liner to check it out. It was white and had the same thickness of Schedule#40 PVC.
I was amazed at the equipment RooterMan had outside my place. The equipment he had cost upwards of $100,000.00. Hi tech stuff that took a technician to run it. There were 3 men and 2 trucks to do the job. And it was completed in two days. Lottsa difference from the old days when I went out on a sewer call with a Ridged K-60 Sewer Machine and a ladder to get to the roof vent. I just wanted to point out that there's another option besides replacing drainage that the years have ruined. If your pipes are a candidate for a reline job I strongly suggest you look into it before you decide to replace the drainage pipes. I did and saved a bundle in addition to keeping my home intact. Just thought I would share that with you all. Regards and thank you for rating my answer, Tom