Our 2nd floor bathroom sink drains down to about 3" of water in the bowl each time it is filled, but won't drain farther. 1st I plunged it (not sure if this is still the recommended 1st line of action or not). Plugged the sink vent hole and black water comes up. (Gets even higher in the sink bowl).

I removed the P trap, and cleaned out what little was in it, and tried to run a snake down the remainder of the drain. It went in about 2 or 3 feet, but I could not get it to go farther. The house is almost 100 years old, by the way. Metal pipes. It was a hand-operated snake - just a coil of wire with a length of metal tube and a set screw. So I probably gave up too soon, but it didn't seem possible to get it to go any farther, although it still turned fine.

I replaced the P trap and tried plunging it again, but no different results. Just slightly cleaner water now. SO when I plug the drain with the built-in plug, and fill it over the level where it will drain down to, and then unplug it, it drains down fast enough to create a small whirlpool in the water. In fact, with the plug un-plugged, the water never gets above a certain level with the faucet on - it seems to drain almost quickly.

Is this simply a partial blockage that has enough gunk to stop a little water, but lets the water out with higher pressure? What is the down side to using a liquid chemical to unblock it? Would I be likely to damage the pipes? We've ahd very cold temperatures here the last week or so - I'm not sure if that could affect it. Or would it be something wrong with the vent pipe?

Thanks

Sounds like a partial clog in drain. Need to get that snake further down the drain. Or maybe use a better snake. It can be very hard to get around the fittings when galv pipe used. I don't recommend using acids to clear drain, but that's just me. They may not only hurt drains(old galve drains) but can be a hazard to you(burns, inhalation).

Have you tried removing the plunger(stopper) and see how the sink drains then. Sometimes the stopper will not open enough to let a good stream of water out of the sink. Try this first, and let me know what you find.

I did try taking out the stopper lever below the bowl. The water drained out into the bucket, but once I put it back together the problem was the same. It seems to be farther down the drain where it's clogged.

Any tips on how to get a snake to go through? It's like it hits a wall 2 or 3 feet in.

I did try taking out the stopper lever below the bowl. The water drained out into the bucket, but once I put it back together the problem was the same. It seems to be farther down the drain where it's clogged. I removed the P trap, and cleaned out what little was in it, and tried to run a snake down the remainder of the drain. It went in about 2 or 3 feet, but I could not get it to go farther. The house is almost 100 years old, by the way. Metal pipes. It was a hand-operated snake - just a coil of wire with a length of metal tube and a set screw. So I probably gave up too soon, but it didn't seem possible to get it to go any farther, although it still turned fine.
Any tips on how to get a snake to go through? It's like it hits a wall 2 or 3 feet in.

You quit too soon. Remove the trap and try again.(see image) You'll run into a bend about 8 inches in the wall but crank and work your way around that and you'll only have 6 more feet to go. Then you'll run into the stack. Flush with a large pan of boiling water. If you still have a clog then you must rent a sewer maching(see image) and snake the lavatory roof vent. Put out enough cable to reach the base and 16 feet more. Good luck and t6hank you for rating my answer. Tom

Well, OK - that sounds like good advice, except that (today - one week later) I tried exactly what you said before I had read this new answer and got to the point where the auger stopped, and kept on pushing on it and cranking it, the best I could. What happened, as near as I can tell is that the snake bent in two, and somehow filled the drain pipe up until I could no longer get any more of it to go in. At that point, I pulled it out and a little bit of very blackened water came out, but not anything like enough to clear the pipe out. I tried once more, with similar results. I tried a home remedy I read about somewhere else - not sure if there is any real value in it - vinegar (and baking soda, but I suspect it's the vinegar that has any chance of working.) I'm waiting about an hour to check and see if it drains any better now. I figured at least it's a weaker acid, and maybe it will work on whatever is in there without taking off too much of the metal while it's at it.

One more thing - noticed this time, as I plunged the sink again (this time to show my daughters who are still young enough to be interested) that the water seems to go into the drain, but actually comes back up when you pull it back out with the plunger. It then does a little dance like it's on a spring. (I theorized it was air in the pipe somewhere, since water does not compress easily) Am I right? You said the vent stack? How do I know the auger is going into it? You think it's the stack that's blocked?

I tried exactly what you said before I had read this new answer and got to the point where the auger stopped, and kept on pushing on it and cranking it, the best I could. What happened, as near as I can tell is that the snake bent in two, and somehow filled the drain pipe up until I could no longer get any more of it to go in. At that point, For openers you need to know what's in your walls. After putting in over 6 foot of snake in the horizontal drain lin the wall you hit the vertical roof vent and who knows which way the snake went. You just spun your wheels!
Remember this from my last post?
If you still have a clog then you must rent a sewer maching(see image) and snake the lavatory roof vent. Put out enough cable to reach the base and 16 feet more. Go up on the roof and snake the lavatory roof vent and you'll clear your clog. Good luck and thank you for rating my answer. Tom