How do I hook up a p-trap to an unthreaded chrome pipe stub?

In houses from that era, that chrome piece is usually a solder bushing or a threaded nipple rather than just a pipe sticking out of a stack. If you look closely at where it meets the wall, there might be a hex nut or a transition joint covered in decades of paint and lime. If you can get a pipe wrench on it—carefully—it might actually unthread from a tee inside the wall. If it does, you can just screw in a new brass nipple and a proper **trap adapter**. That is the cleanest way to do it and avoids the headache of trying to clamp onto a tiny stub. If that pipe is truly solid or you’re worried about snapping it off inside the wall, you’re stuck with that 3/4 of an inch. A standard slip-joint nut and washer definitly won't have enugh surface area to grab onto securely. Your best bet in that scenario is a shielded **rubber coupling**, often called a Fernco. But honestly, 3/4" is really pushing the limits for a reliable seal. If you go this route, you have to clean that chrome pipe down to the bare metal with emery cloth so the rubber has the best possible friction.

You might be able to gain a little more room by ditching the escutcheon plate temporarily to see what's behind it. Sometimes those plates are thick or sitting on a mound of old plaster and tile grout. If you can chip away just a tiny bit of material around the pipe without cracking the visible tile, you might get enough clearance to seat a coupling properly. Just be gentle; those old pipes can be brittle once they start corroding from the inside out.

And make sure you don't install the new p-trap backwards. The deep curve shold be at the bottom, with the shorter side connecting to the sink tailpiece. If the heights don't line up perfectly with the wall drain, use a tailpiece extension instead of trying to tilt the trap at a weird angle. Forcing a fit on a short stub like that is just asking for a leak a month down the road.

I'm in a similar spot with my old sink. If I try a pipe wrench to see if it unthreads, how much force is 'too much' before it snaps? I'm terrified of breaking somthing behind the tile and turning this into a total nightmare. Has anyone tried internal pipe wrenches for this? I've seen them for shower arms, but I’m worried it might just crush an old chrome pipe. Also, if I end up using a rubber coupling, are there extra-deep covers to hide the metal clamp? Those Ferncos aren't exactly the look I'm going for in a guest bath.

Watch out with those internal wrenches on 1-1/4" chrome. If it's old thin-wall brass, those teeth will just shred the inside or flare it out like a trumpet, making it impossible to seal later. If you've only got 3/4" of pipe, check if it's actualy copper or brass under the chrome. If it is, and you're handy with a torch, you can sometimes sweat a 1-1/4" female adapter directly onto that stub. It’s a permanent fix and way more reliable than a rubber boot when you're working with almost no surface area. Just keep a damp rag behind the pipe so you don't scorch the tile or the framing.

If you go the Fernco route, be careful when you're tightening those stainless clamps. Those 1-1/4 inch chrome pipes from that era are often thin-walled brass, and after 80 years, they can be as soft as a soda can. I've seen guys crank down a clamp on a short stub and it just folds the pipe in on itself beacuse it's so corroded from the inside. Also, check if the pipe is still perfectly round. Sometimes they get slightly ovaled from decades of weight or old repairs. If it’s not a perfect circle, that rubber coupling is going to weep no matter how much you clean the metal.