I looked into the trenchless options, they don't really work for our scenario. First, the existing line might not be in good enough condition to support trenchless replacement. Also, while we can dig a whole at the city side, the lines terminate under the slab so there's no way easy way to create an entry point for the new line. There's also several joints under the slab, and we'd have to tear out the driveway to get to the existing line on one side. So far, our estimates are $12k (to tunnel to the two known breaks and replace only those portions) or $20k (to tunnel the entire width of the house and replace the entire system). A SEPARATE OPTION: I'm admittedly no expert, but I see a way to run two new lines - one up each exterior wall) which would serve the entire house with minor tunneling. The disadvantage is that the sewer line wouldn't be under the house, it would be buried under the strip of grass on either side. One company says they wouldn't do it that way because the line isn't protected by the house and could break more easily. To that, I say that if it breaks, it would be a MUCH easier fix than if a line were to break under the slab again. Is there any reason a new line can't be run outside the exterior walls of the house?

"All houses of your vintage had terracotta/clay pipes etc and will all eventually need to be repaired or replaced." WRONG!!!!!!!!!!! The post says the house is 30+ years old. Both PVC & ABS pipe have been available and in common use for 50 years. In addition, there was concrete hub&spigot SV pipe, Borosilicate glass pipe, vitreous clay pipe and orangeburg pipe. The post also says the problem is a low point in the pipe where water is colleting. That standing water causes two very distinct problems. 1. It creates a trap between the house and the sewer which prevents the movement of vent air. 2. The standing water creates a barrier which restricts the velocity of flow which then causes solid particulates in the waste water to settle and collect forming clogs. Neither of these conditions would be remedied by religning the pipe as was suggested by Alexbar001.

Out of curiosity I just called my local Lowes store to see what the cost difference would be to use 4" PVC-Sched40 as opposed to 4"PVC-SDR35 and I was utterly amazed at the results. A 10' length of 4" PVC-SDR35 is $15.03 A 10' length of 4" PVC-Sched.40 is $14.67 If we then factor in the cost of a 4" PVC coupling the price is almost identical. Considering that the trenching cost remains the same regardless of which pipe you choose the savings is then only the time required to make a slip joint versus apply primer and glue however, while Lowes only carries 10' lengths PVC sched.40 is principally made in 20' lengths available at any Plumbing supply house. This means you only have half as many joints with sched40 so the actual labor time would be nearly the same. Bussdriver is correct that they do use PVC SDR pipe with gaskets joints for municipal mains however it must be remembered that the SDR standard was originally used to specify concrete sewer pipe. When we apply the SDR formula to a 36" municipal main we get a wall thickness of 36/35= 1.02". Even an 18" municipal main would have a 1/2" wall thickness. The smallest diameter PVC-SDR35 pipe used for municipal mains is 8" which would have a wall thickness of 8"/35= 0.228' which is approximately the same thickness as 4" PVC-sched40 at 0.237". However when we consider that a residential house sewer is limited to 3" or 4" we then get a wall thickness of 3"/35= 0.085" or 4"/35= 0.11". While PVC-SDR35 is approved in both the IRC and UPC most local codes do not approve it because as the pipe ages it will become brittle and when it is put under the stress of tree roots of rocks in the soil quite often the pipe wall will shatter in the same manner as vitreous clay tile. Don't believe the pipe wall is brittle, go to your local hardware or home supply store and examine there stock. Look for the lightweight light green or white pipe with preformed end bells. It will be labelled PVC-SDR35 on the pipe wall. Now look through the stack and see how many sections have broken end bells or chunks missing on the raw end.

you may not know but this pipe lining ws started over in europe the last 3 decades maybe 4? their infrustucture is way older than ours. where I am, it is all slab homes (no basements) mostly 1970's and 80ty's were made of cast iron. PVC started to make it way into the mainstream after that. These pipes are rotting away! when I say rotting I mean the base is gone.fractures are 1/2 inch and wider that are all over the place.sides,bottom, top, in lentghs that are in feet. Now you also have water lines in there.where? who knows. pipe bursting is not good because at every place a 2" or 4" pipe comes into the main line you have to dig up a section of floor to have a repair done et every interval. short of digging up the home and it had been done, pipe lining is the only real way to avoid a total rehab of the home. the co's that do this have a limited 50 year warranty on materials. it seals every joint,fracture all drains coming into the line and thats where they call reinstateting comes in. they have to open up all drains that where covered over by the material. so if europe started this,30 or 40 years ago and did all their streets (no digging up the streets all over europe) and I have not read anything bad happening I would not have any fears. like anything else,price and convience,where I am located sarasota fl this is the only way to fly! I am talking infustructure. if you had a cobblestone driveway the cost of lining would be cheaper than having someone come in to do the repair on top of the repair. also pipe pulling would in that case should be looked at too. BTW I also do this work