My home was built in 1965. Recently, a slowly draining bathroom sink was found (on rotor-rooting) to be obstructed by soft mud, leading our plumber to conclude that drain pipe under foundation was broken. He proposed tunneling under foundation (about 40 feet, then to include 15 foot detour to include kitchen drain) , to replace all drain pipes from bathrooms/Kitchen to main drain, then install 8 piers to support foundation, then replace dirt and concrete over access area. Estimated cost of $48,000 seems excessive. Your thoughts?

  • 1
    A plumber is not a structural engineer and he cannot give you viable advice on how you properly support an excavated foundation. Even if you were to allow the work he recommended you must seek approval from an engineer.
    – Matthew
    Commented Sep 19, 2014 at 17:51
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    If the sink now drains and they charged you $100 to root it, have it done once a year for the next 480 years. Is the foundation sinking or dirt in the yard becoming displaced? Then you should worry, or buy some dirt.
    – Mazura
    Commented Sep 20, 2014 at 1:18

2 Answers 2


I would never, under any circumstance allow someone to tunnel under my house. Anyone in proposing this is a complete moron. It's a drain pipe that is probably 6-10 inches wide.

The normal solution - which I have done 20+ times for clay pipes in my area - is to break apart the concrete above the drain pipe, dig it out, replace. While we are inside we try to replace the drain line about 2 feet to the outside... this part is a b*tch - but point is digging up some home right by the foundation on the outside presents problems too.

If the first floor or basement is finished then you have to pull up carpet, go through tile, pull up wood floors - do whatever you need to do. On the wall you might have to remove small sections temporarily.

So costs:

  • Digging 3 foot wide section above drain + kitchen area (not sure what the scope is there). This can be done by two day laborers and a jackhammer in one day. Let's say high end $800 - I will give you price that guys would be smiling about after in my area.
  • bin to throw away trash/concrete - $300
  • removal of walls (maybe just bottoms) - $500
  • actual plumbing work - 2K-3K
  • backfill of area and concrete work - 1-1.5K
  • flooring??? that is the big question - somewhere between $200 (carpet) and 4-5K
  • redoing walls - this depends too on how many and what the layout is - $500-3k

On low end maybe 8K and high end 15K. And when I say low end that is a high first bid that would make contractor happy and 15K is spending a lot of flooring and wall finishes. I just replaced an old clay drain from last remodel. This city let me do my own plumbing (some do some don't), the city had 3 inspection checks, I paid a crew for excavation and concrete work (I did nothing hard), it took 4 days, and costs me right at 3K for permits, materials, and crew. We had to go about 50 feet from main stack to exit point - through two walls and a finished basement (carpet).

Now I want to mention something else that is becoming more popular in our area yet I have not used it because of costs. There is technology where they can run a sleeve inside of existing pipes that creates a permanent solution. I have been quoted around 8-10K for these and they just didn't make sense for the money because we can do it cheaper - in my area it is all basement so there usually isn't much cost beyond concrete removal and repair. I am sure someone else on here can weigh in on this.

Another thing to think about too... Is if you are going to have this kind of work done I would really think hard about what else is under your house and do you need any other work done. If you have electrical, other plumbing, hvac, whatever under there really think if you see any need to change or upgrade anything. You don't want to do this every 5-10 years and once you get the process going, doing something extra now will be a fraction of the cost in the future.

  • The sleeve mentioned is actually pretty neat but longevity is unproven (they will guarantee no roots for 10-15 years). They can use it for lines with breaks too. I do not think it works for cast iron, just clay. Commented Sep 19, 2014 at 20:12
  • @JimmyFix-it - Those are good points. I am not sure about cast iron. I guess it would work if there wasn't rust build up in the pipes but yea I can't see clean cast iron more than 5 years old. They guarantee 20 years by me. That alone would make me choose PVC if cost was similar - even if I won't be in the home in 20 years. But I really think the sleeves are for more urban environments where doing something might cost a lot more.
    – DMoore
    Commented Sep 19, 2014 at 20:21

$48,000? Challenge the findings. Tell them to scope it and show you the video, pay them for a DVD. Then get a second and third opinion.

Ask them the cost to just dig up and fix the exact area of concern (instead of all the pipes). Whatever that price is will still be too high so tell them you cannot afford it and ask what is the bottom line cheapest price to fix it.

I am assuming concrete slab floor, instead of tunneling just cut the slab at the point of the break and excavate. Even if you have to move or remove cabinets, open walls, and replace flooring, it will not add up to $48,000.

I have a slab floor house built in the late 50's, during a remodel we cut the concrete and dug up and replaced all the old buried cast-iron drain pipes. It was messy, took a while, and we had to pour concrete afterwards, and replace flooring and carpet. The cost was a fraction of your figure, including all the materials, concrete, flooring, labor, and the rental on the concrete saw.

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