Thoughts on snaking vs. chemicals for old galvanized pipe?

I had the exact same setup in my 1968 ranch. Those old galvanized lines are notorious for closing up because the rust expands inward, often leaving a drainage hole about the size of a pencil. I was terrified of using my General Pipe Cleaners hand auger because I’d heard those horror stories about pipes being paper-thin. Instead of going nuclear with a snake right away, I tried a hot water flush followed by a heavy dose of Thrift T-600. It’s a lye-based crystals drain opener that is usually safe for old metal if used correctly.

If you do decide to use that 1/4 inch snake, keep it very light. Don't use a power drill attachment. Feel for the resistance; if it feels like you're hitting a solid wall rather than a soft clog, back off. Usually, the sludge in these old pipes is more like wet concrete than a simple hair clog. If the Thrift or a similar product like Bio-Clean doesn't open it up after a few treatments, you might be looking at a localized blockage at the San-Tee junction behind the wall. I ended up having to cut a small access hole in my vanity back and used a Fernco coupling to replace just the accessible section with PVC, which saved me from ripping out the whole slab.

I've wasted weeks trying those enzyme cleaners and hot water flushes on my 1970s galvanized lines, and honestly, they do nothing for actual scale. That 'pencil-sized hole' people talk about is ussually hard as rock. If the pipe is so thin that a 1/4-inch hand snake punctures it, then the pipe was allready failing and was going to leak behind your wall next month anyway. Better to find out now while you're already looking at it than during a surprise flood. I eventually grabbed a Ridgid K-45 and worked it slowly. Don't just jam it in; feel for the resistance. You can usually tell when you're hitting a blockage versus a bend. If you pull back a bunch of black, greasy sludge and rust flakes, you're making progress. But if the snake just spins and the water doesn't move, that pipe is likely toast. At that point, stop messing around and cut into the drywall to replace it with PVC. It's a weekend of work, but it beats worrying about a ticking time bomb every time you brush your teeth.

First thing I noticed is that flex tailpiece. Get rid of that accordion-style junk; those ridges catch hair and soap scum faster than anything. As for the galvy, if you’re scared of the snake, we used to use a blow bag or a Kinetic Water Ram back in the day. It uses a slug of compressed air to move the blockage instead of scraping the pipe walls thin with a cable. If you can't get a shockwave to clear it, that pipe is likely choked with mineral scale all the way to the main. At that point, stop wasting your breath and start thinking about a new run of PVC.

If you're alredy at the point where you're worried about the pipe integrity, skip the chemicals and get a General Pipe Cleaners Super-Vee. It gives you way more control than a cheap hand snake, and the Power-Prehension chuck keeps you from over-torquing and blowing trough a thin wall. I saved a 1950s steel line last year using it with a 25-foot Flexicore cable. The inner core prevents kinking, so you're actualy cleaning the grease out instead of just whipping the pipe. If that Super-Vee doesn't clear a path, then you'll know for sure the galvanized is too far gone and it's time for the sledgehammer.

Don't count on that 1/4 inch snake doing much besides spinning in circles. If the galvanized is that far gone, you'll probaly feel it 'crunching' when you're in there. I'd pull the sink away from the wall and look at the threads where the pipe enters the wall. If those threads are crumbling or rusted out, you're toast. I've had luck using a wet/vac to suck the gunk out instead of pushing it further down. Sometimes pulling that sludge back towards you is safer than trying to force a hole thru it.