I have a slab house built in the 1950's with cast iron lines in the concrete slab. We are doing a total remodel and so have access to all the fittings above the floor and want to switch them out to plastic.

Once we have the pipes open, I want to have a camera run through the remaining pipe below the slab to verify that all looks well. The drains have been operating without any issues.

I had one plumber suggest that since I wanted to get a city permit for the plumbing work that he would want to cut open the concrete and replace all the piping under the slab. He stated that would be the only way to have it hold pressure and have the work pass the permit process.

why not come in from overhead instead? I've done this on several houses with the gray poly.

As a plumbing contractor and owner of 7 old homes on a slab, I've had to replace several drain lines under the slab. There are several methods. When I've had plumbing near outside walls, I re-ran the lines from under the slap to the outside and run new sewer lines along the property that then tied into the old line going to the sewer system.

Hold pressure? are you talking fresh water lines or sewer? The only pressure tests I 'm aware of are for gas lines or fresh water, not sewer.

I wouldn't replace just the above the slab pipe. If it's bad above then it's bad below. Having new pipe above will not keep you from having to gut it again to replace the lines below the slab.

If there is a problem found - or if you just want to be proactive while it's torn apart, I suggest: Rather than breaking up the slab, check out the liners that are available today - perhaps what Robert was referencing. They can make the inside of the old pipe like new, easier & quicker than jackhammering the slab, re-pouring it, and all that.

When water comes up from a crack in the slab when water is draining from a fixture such as a bathtub or washing machine the condition of an under the slab drain pipe is called into question.

I could do a pressure test. Check to see if the sewer main is blocked and drill some test holes in the slab to determine the distance and amount of water under the slab. I can also camera the line and use colored smoke while plugging the air stacks, drains and sewer line outside the structure.

Some or all of the above I can do myself as a plumbing contractor. I investigate, test and determine what the problem is.

One time I used a 4 foot long "pipe liner" and inserted it the sewer line and inflated it -- letting the epoxy to form around the liner and forming a pipe inside the old pipe. Then after 2 hours removed my expanding balloon. This method only costs a few hundred in materials but takes specialized equipment.

Several clients had sewer failures under a driveway with their clay sewer main. Instead of breaking and and removing the driveway to access and replace the sewer line I simply installed in interior liner and a closer clean-out.