Is it normal for a plumber to insist on digging up the floor instead of just cleaning the pipes?

The plumber is telling you the truth because once those old cast iron lines scale up to the point of a pinhole, there isn't a spray or a chemical in the world that will save them. You're looking at decades of tuberculation—basially rust and mineral deposits that grow like barnacles inside the pipe until there's no room for water. Hydro-jetting is the common non-invasive suggestion people look for, but on pipes that thin and fragile, high-pressure water often just blasts a hole right through the rotted bottom of the line.

There is a process called **Cured-In-Place Pipe (CIPP)** or pipe lining where a resin-soaked sleeve is pulled through, but it requires the original pipe to have enough structural integrity to act as a mold. If yours is as choked off as he says, they’d have to run a mechanical descaling chain through there first to clear a path. With cast iron that old, the descaler usually just finishes the job the rust started and collapses the whole run, leaving you with a collapsed pipe anyway.

Biting the bullet on the trench is miserable for a few days, but it's the only way to guarantee the pitch and grade are actually correct. When you swap to PVC, you’re getting a smooth-wall surface that waste simply won't cling to. No more snagging toilet paper or grease traps. Most crews will jackhammer a neat line, swap the pipe, and have fresh concrete poured back over it within forty-eight hours. Make sure they use **Schedule 40 PVC** and check that they're replacing the sub-slab fittings too, not just the straight runs. Once the dust settles and you can finally run a heavy load of laundry without staring at the floor drain in fear, you'll realize the peace of mind is worth the mess. It's one of those "buy once, cry once" home repairs that actually fixes the root cause forever.

Have you actually seen the camera footage for the entire run yourself? I’d be a bit wary if he’s recommending a full-scale dig based on just one blockage point. Sometimes these guys see a bit of scale and jump to the nuclear option, but have you ruled out a localized repair? It's possible only a small section is failing while the rest is serviceable.

Also, did he check the vent stacks? If those are restricted, it can make a decent pipe drain like it’s choked off. Might be worth getting a second camera tech out there just to verify the whole line is actually toast before you let them start jackhammering.

You're right about biting the bullet on the full replacement. Once that cast iron gets to the 'pinhole' stage, the bottom is ussually paper-thin anyway. One thing to make sure they do while the floor is open is to use a bed of crushed stone or pea gravel under the new PVC. A lot of those old lines were just tossed in the dirt, wich is why they settled and lost thier slope in the first place. Properly bedding the pipe prevents it from sagging later on, and it’s way easier to do now than trying to fix a belly in the line five years from now.

If you're going to tear up the slab, don't let them cheap out on the transitions. Make sure they’re using the heavy-duty Fernco Proflex 3000 series shielded couplings to bridge the new PVC to any remaining iron. Those thin rubber bands won't hold up under the weight of the fill.

Also, tell them you want a Mainline Fullport backwater valve installed while the line is exposed. It’s an extra $200 in parts but it’s cheap insurance against city sewer surges. Go with Charlotte Pipe Schedule 40; don't let them grab the cellular core stuff from a big box store. Solid wall is the only way to go for sub-slab.

One nuance many homeowners overlook til the first flush after a renovation is the significant increase in acoustic transmission when transitioning from dense, vibration-dampening cast iron to thin-walled PVC, so you might consider wrapping the new runs in some high-density mineral wool or specialized pipe insulation if the sound of rushing effluent trough the slab will bother you. Furthermore, please verify that your contractor is utilizing solid-wall Schedule 40 PVC rather than the lighter-weight cellular core—often labeled as "Co-ex"—which, while technically permitted by some local codes for DWV, lacks the same long-term crush resistance and structural rigidity required for burial beneath a poured concrete slab where future settling coud occur.