Author Topic: Replacing rusted cast iron sewer line under house  (Read 1886 times)

Bobberth

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Replacing rusted cast iron sewer line under house
« on: February 22, 2017, 03:12:54 PM »
I bought a 90 year old rental property and like most properties in the area, the cast iron sewer line under the house needs replaced. The clay pipe outside of the house running to the main sewer is fine. The top of the cast iron has oxidized. These have been running me +/- $3000 to repair. The guy I used would take 3 days to do the project-Day 1 he brings in unskilled workers to break through the floor and dig up the pipe. Day 2 he comes in and runs the pipe. Day 3 unskilled workers come back to fill in and finish floor. Seems like this job would be easy to do on my own as it's mainly grunt work.

I have about $200 in PVC pipe and fittings replicating what was there. I bought a Harbor Freight jack hammer for $300. Cement to patch back up the hole will be less than $100. I am looking at significant dollar savings if I can pull this off. If the jack hammer last for more than just this property:  Bonus!

I have done PVC piping above grade but I'm a bit nervous doing this because of the waste part-the other jobs were sinks, baths/showers or washing machine drains. We were able to remove the old cast iron without digging under it so, theoretically, we should be able to lay the new pipe and have it be the same grade and functionality as before. I know the 1/4" slope per 1' rule but the first 10' of piper was steeper that this. That 10' goes from the stack to a 45* elbow and then straight all the way to the main sewer. My guess is this extra slope is to help the waste make the only turn. I could raise (lower?) the slope to meet the 1/4" rule, but eventually I need that slope to meet up with the existing clay pipe anyway. And I figure if it worked before, it will work now?

Does anybody have any tips or tricks or suggestions to keep in mind while doing this?

paddedhat

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Re: Replacing rusted cast iron sewer line under house
« Reply #1 on: February 23, 2017, 04:53:08 AM »
When it comes to waste piping pitch, there are the rules, and there is observed reality. I have plumbed dozens of new homes, and done lots of repair and renovation. In that time I have seen multiple examples of pipe installations that, according to the rules, should be nothing but a clogged mess, yet function flawlessly for years.  Particularly, if its ABS, or PVC pipe, which apparently is slippery enough, that it works when logic tells you it simply can't.

On several occasions I have seen long horizontal runs of pipe heading off to a fixture with no support other that the fact that it's hanging off a trap under a sink. Over the years the vertical run to the trap slides down, and the run develops a noticeable negative pitch. I have even asked a homeowner if the sink ever clogs? never heard a yes.

At some point, decades ago, my house was totally re-plumbed with plastic drainage. The installation is a joke. The toilet had a horizontal run with a 3/4" negative slope for a few feet. The sink has a 15' run of 1-1/2" in the floor joists that is unsupported. It sags down dramatically in several places, and by all the rules, should never work. It's trouble free. There is a ten foot section of the main 3" run that is pitched at 15-20* or so. I just bought the place, but I'm not surprised in the least that there are no drainage issues.

In your case, you are replacing a cast soil line that wan't installed "by the book" almost a century ago, yet performed just fine. You are replacing it with a product that is far smoother inside, and far less likely to develop obstructions as it ages. There is no reason to do the extra work of "correcting" something that works just fine. Pull the old stuff out, glue the new stuff together, connect it to the cast with a Fernco coupling, and you're done. Once you get this one done, you will be a bit shocked at how easy it actually is. Good luck.

Bobberth

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Re: Replacing rusted cast iron sewer line under house
« Reply #2 on: February 23, 2017, 02:36:30 PM »
Thanks for sharing your experiences! It takes some of the worry away but I still have the 'first time' nerves like I do every time I try something new. I keep going over everything that needs to be done in my head and it really shouldn't be a big deal to do. Which makes me more nervous that it could really be that simple.

paddedhat

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Re: Replacing rusted cast iron sewer line under house
« Reply #3 on: February 23, 2017, 03:19:22 PM »
Thanks for sharing your experiences! It takes some of the worry away but I still have the 'first time' nerves like I do every time I try something new. I keep going over everything that needs to be done in my head and it really shouldn't be a big deal to do. Which makes me more nervous that it could really be that simple.

My sophomore physics prof. had quite an impression on me. He introduced me to the concepts of KISS, which is "keep it simple, stupid", and to the concept of avoiding "paralysis by analysis".  Both ideas can be pretty valuable in situations like this. Good luck, you will be fine.

lthenderson

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Re: Replacing rusted cast iron sewer line under house
« Reply #4 on: February 24, 2017, 07:44:42 AM »
My sophomore physics prof. had quite an impression on me. He introduced me to the concepts of KISS, which is "keep it simple, stupid", and to the concept of avoiding "paralysis by analysis".  Both ideas can be pretty valuable in situations like this. Good luck, you will be fine.

In addition to those two, I had a professor that always said, "Don't get lost in the forest because of the trees."

MandyM

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Re: Replacing rusted cast iron sewer line under house
« Reply #5 on: February 24, 2017, 08:14:53 AM »
Were you thinking about reducing the slope between the stack and the elbow to meet the 1/4" per foot? Or were you saying that the slope after the bend was flat?

Either way, I agree with paddedhat - 1/4" per foot is overkill to move the wastewater - that is approximately a 2% slope. Out in the street we use a 0.4% minimum slope on 8" pipe and it goes down as the pipe gets larger. The higher slope requirement is due to the smaller diameter (higher likelihood of a blockage), the difficulty of access for repair, and the consequences of a blockage (possible overflow in the home). So you may skimp on your safety factor, but probably not much. And the smoothness of the new pipe probably overcomes that anyway.

The reason that a bit of negative slope isn't generally a problem is because the water will build up, but eventually flow the direction you want it. So the sag or belly might hold a little water, but that is it. It will only cause a problem if it is severe and then sediment gathers to completely block it (like a clogged P-trap). Technically, it reduces the pipe capacity too, but the pipe is way oversized in relation to capacity anyway (to allow for solids).

"Freedom lies in being bold." -Robert Frost

Spork

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Re: Replacing rusted cast iron sewer line under house
« Reply #6 on: February 24, 2017, 08:45:20 AM »
I didn't do it, but I've had it done. 

In my case the "belly" was actually WHY I had it done.  Cast iron pipe running across the house under a slab foundation.  The dishwasher was upstream.  Since it was cast iron, the stuff that sat in the belly rusted the pipe out.  Add a little dish washing detergent, which is very caustic, and you'll eventually have no pipe.  This might not occur with PVC, but a belly will likely still allow crud to build up.

As mentioned up thread... support it.  The plumber used pipe hangers anchored to the foundation above.  This was a pretty massive amount of work for 3 days and a crew of about 4.  Very messy if you are going through the center of the slab.

This is about a 15 foot tunnel.  The camera has terrible depth of field.



Very messy inside:
Some will sell their dreams for small desires
Or lose the race to rats
Get caught in ticking traps
And start to dream of somewhere
To relax their restless flight

Jon Bon

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Re: Replacing rusted cast iron sewer line under house
« Reply #7 on: February 25, 2017, 12:55:54 PM »
I didn't do it, but I've had it done. 

In my case the "belly" was actually WHY I had it done.  Cast iron pipe running across the house under a slab foundation.  The dishwasher was upstream.  Since it was cast iron, the stuff that sat in the belly rusted the pipe out.  Add a little dish washing detergent, which is very caustic, and you'll eventually have no pipe.  This might not occur with PVC, but a belly will likely still allow crud to build up.

As mentioned up thread... support it.  The plumber used pipe hangers anchored to the foundation above.  This was a pretty massive amount of work for 3 days and a crew of about 4.  Very messy if you are going through the center of the slab.

This is about a 15 foot tunnel.  The camera has terrible depth of field.



Very messy inside:


Mother of god, did you hire a family of dwarfs?

Am I understanding you tunneled under your slab like you were smuggling drugs under the boarder?!!

There was no better way? Did this cost your entire net worth or 2x your net worth?!


Spork

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Re: Replacing rusted cast iron sewer line under house
« Reply #8 on: February 25, 2017, 03:50:54 PM »


Mother of god, did you hire a family of dwarfs?

Am I understanding you tunneled under your slab like you were smuggling drugs under the boarder?!!

There was no better way? Did this cost your entire net worth or 2x your net worth?!

We joked that we hired the cast of Hogan's Heroes.  And yes, they made a 15ft or so tunnel under the slab.  This was by far NOT the most expensive part of the project or the most destructive.  This was a sewage leak under the slab that had gone on for quite a long time in an area of highly expansive clay soil.  The most expensive part of the project was fixing the heaved foundation.  There were 20-something piers installed (many of them IN THE CENTER OF THE DAMN HOUSE!) and another 20 or piers adjusted (from a previous fix).

The week before they dug that damn tunnel, the inside of the whole house was full of dirt from digging piers.  Here's that same living room:



I believe the whole project was about $20k.  That's foundation, plumbing and then repairing the flooring, patio, tile, etc that got destroyed.  (I did all the repair work.)

On the plus side: I got a free shovel out of the deal, so ... there is that.
Some will sell their dreams for small desires
Or lose the race to rats
Get caught in ticking traps
And start to dream of somewhere
To relax their restless flight

blub

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Re: Replacing rusted cast iron sewer line under house
« Reply #9 on: February 25, 2017, 04:36:07 PM »
I believe the whole project was about $20k.  That's foundation, plumbing and then repairing the flooring, patio, tile, etc that got destroyed.  (I did all the repair work.)

Yikes. Would you buy/have you bought a house on a slab in Texas again?

Spork

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Re: Replacing rusted cast iron sewer line under house
« Reply #10 on: February 25, 2017, 04:51:35 PM »
I believe the whole project was about $20k.  That's foundation, plumbing and then repairing the flooring, patio, tile, etc that got destroyed.  (I did all the repair work.)

Yikes. Would you buy/have you bought a house on a slab in Texas again?

Short answer: yes.

Long answer:
* That house had a ton of problems.  I learned after the fact that this was a builder's son's first attempt at being a general contractor.  The craftsmanship wasn't very good. 
* I don't live in the Dallas area any longer.  The soil elsewhere isn't that nasty expansive black clay.  In DFW, foundation work isn't uncommon.  Where I am now (in sandy soil) I can't think of anyone I know that's had it done.  My parents' home is on a slab over 50 years old and hasn't moved a bit.
* Pretty much anything built in Texas (and probably much of the south) is going to be on a slab unless it's from the 50's or earlier (and then it is pier and beam).  Yes, there are exceptions, but it is hard to find someone that does any pier and beam work any more.  Slabs are cheaper, too.  It is very rare to find a home built on footings with a basement because the freeze line is shallow and no one wants to pay for it.

Slabs absolutely suck for repairs.  I swore I'd go pier and beam.  But when we shopped it, we didn't like the prices.
Some will sell their dreams for small desires
Or lose the race to rats
Get caught in ticking traps
And start to dream of somewhere
To relax their restless flight

Bobberth

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Re: Replacing rusted cast iron sewer line under house
« Reply #11 on: March 01, 2017, 01:58:19 PM »
I did it. I didn't sleep much Friday night going into the job as I kept thinking it through in my head about what to do and where is the best place to start and then what would come next.... Everything was dug out already going into the job so I was able to start Saturday morning assembling the PVC. I shoved about 7' of 4" PVC into the clay pipe and will cement around where the pipes meet (weekend lows were going to be below freezing so I haven't done any concrete yet). It took about 2 hours to assemble the PVC. Overall, everything went well. I had to use 2 couplings as I was a little off on my lengths going into a 45* turn. The height of the 2 floor drains are going to make me nervous until the cement is poured and I can verify they (hopefully) work.

It's hard to say how much time is in this project. My brother in law moved in with us so I had him bust up the concrete and dig out the pipe except the last 6' or so until the clay pipe. I dug that out myself so I could examine how the clay & cast iron connected. It took about 2 hours at night, after work, to dig that last section out. My estimate for future projects is that it would be a 3-4 full day job for just me. 1-2 days to bust up concrete and dig out pipe. 1 day to lay new pipe and fill in hole and 1 day to do concrete. A second person would definitely take at least a day off of that. A vacant property wouldn't be a problem. An occupied property that needs to be finished quickly might still need to be hired out.

Currently I'm about $250 in PVC parts. That includes a new P trap for the basement sink and I have about $20-$30 in extras to return. With the cold weather this weekend I went back and bought the expensive All Weather glue to insure there wouldn't be problems. That doubled the price of glue. I'm at $80 of concrete right  now. Will have to see if I need more or will take some back. The jackhammer was about $330 after a 25% off coupon at Harbor Freight. With everything, it will be about $650-$700 for a job that would have cost around $3k to hire out. The jackhammer will be able to be used on future projects as well. That means future sewer replacements would cost around $300-$400 and a weekend or two of a good workout. Definitely a winner. Thanks for everybody's input!

paddedhat

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Re: Replacing rusted cast iron sewer line under house
« Reply #12 on: March 01, 2017, 02:38:02 PM »
Nice! It's amazing how some trades have no hesitation quoting massive estimates once the project is perceived as moving from the DIY column to the "no way in hell I could ever handle something like that myself" side of the page. I was talking to a neighbor recently, and nearly gagged when he reported how much they spent to deal with failed waste lines in their front yard. They had two pipes replaced from the house to the street, which is less than 40' away. They paid $20k.  Holy Shit. With a rented track hoe/ with operator, two guys, all material, inspections, and two days of work, it didn't cost the contractor over $5K.  Like the tappet bros. used to say, SOMEBODY needs to make that boat payment..................