Hi, I've got quite a situation going here. I own a townhouse, and have a second floor bedroom/bath that is rarely used. About a week ago I went into that bathroom to discover that the sink was full of a coppery colored water, and sediment coated the sink. Apparently it had also overflowed at some point because there was a stain on the floor and the inside of the vanity was very wet. All my other sinks, showers, tubs, etc are draining fine. Anyway, this sink hadn't even been used in months and the water is coming up out of the drain, not from the faucet. I plunged it, I snaked it, and the water wouldn't budge, just kept rising. I did determine that my ac condensation line from the roof runs into that sink line, so I disconnected it at the drain (It was hooked on to a little branch coming off the pipe just above the trap), ran that line into a bucket and let the excess water drain out of the sink into the bucket. Less than an hour later, warm coppery water came gushing out of the open branch on the drain, and with such force that it also filled up into the sink again. This was enough water to completely flood my bathroom floor, vanity, and fill more than half of my bucket once I got it under the gusher. I reconnected the ac drainage line and got a plumber out. He snaked the drain three times and the vents twice and found no blockage, so as a temporary measure to keep the sink from overflowing while I'm at work, he cut the ac drain line up on roof and I've got it draining into my gutter now. But the water level in my sink is still fluctuating. While the plumber was here we found out my next door neighbor, whose unit is a mirror image of mine, was having the same problem in his guest sink. Those two bathrooms share a common wall and the plumber thinks the drain lines tie together at some point and the blockage might be below that. He suggested we try to obtain building plans so he or another plumber could better understand how the lines are tied together. So after three days my neighbor says his sink is draining again, albeit very slowly, while mine is still filling up with water. I apologize for the length of this post, but can anyone offer a suggestion or possible cause for this problem? I should add that the water does not smell, and about two weeks ago both myself and my neighbor's mother, who was staying with him, heard a very loud belching sound in the wall. Thanks.

Hi, I've got quite a situation going here. I own a townhouse, and have a second floor bedroom/bath that is rarely used. About a week ago I went into that bathroom to discover that the sink was full of a coppery colored water, and sediment coated the sink. Apparently it had also overflowed at some point because there was a stain on the floor and the inside of the vanity was very wet. All my other sinks, showers, tubs, etc are draining fine. Anyway, this sink hadn't even been used in months and the water is coming up out of the drain, not from the faucet. I plunged it, I snaked it, and the water wouldn't budge, just kept rising. I did determine that my ac condensation line from the roof runs into that sink line, so I disconnected it at the drain (It was hooked on to a little branch coming off the pipe just above the trap), ran that line into a bucket and let the excess water drain out of the sink into the bucket. Less than an hour later, warm coppery water came gushing out of the open branch on the drain, and with such force that it also filled up into the sink again. This was enough water to completely flood my bathroom floor, vanity, and fill more than half of my bucket once I got it under the gusher. I reconnected the ac drainage line and got a plumber out. He snaked the drain three times and the vents twice and found no blockage, so as a temporary measure to keep the sink from overflowing while I'm at work, he cut the ac drain line up on roof and I've got it draining into my gutter now. But the water level in my sink is still fluctuating. While the plumber was here we found out my next door neighbor, whose unit is a mirror image of mine, was having the same problem in his guest sink. Those two bathrooms share a common wall and the plumber thinks the drain lines tie together at some point and the blockage might be below that. He suggested we try to obtain building plans so he or another plumber could better understand how the lines are tied together. So after three days my neighbor says his sink is draining again, albeit very slowly, while mine is still filling up with water. I apologize for the length of this post, but can anyone offer a suggestion or possible cause for this problem? I should add that the water does not smell, and about two weeks ago both myself and my neighbor's mother, who was staying with him, heard a very loud belching sound in the wall. Thanks.


You don't need a set of plans to tell you that your bathrooms share a comon drain and vent. If the plumber wants to know how the lavatories are tied together inform him we use DWV Cross with 2" branches for the lavatory drains and the two bath room groups share a common vent off the top end of that cross. And he's correct. The blockage's downstream of the two lavs.Which means he missed the blockage all three times he snaked the line out. I would say try snaking from the trap but all he would do is run the snake from one lav and come up in the neighbors. He'll have to locate the correct vent and snake from there. Good luck, Tom

Hi Tom, and thanks for your reply, I really appreciate it. I'm a new homeowner and I'm trying to figure out how things work. I'm sure this theory is probably insane, but if you have the time I'd love your feedback. The drain began backing up shortly after I had my rooftop ac unit replaced at the end of June. I have already determined that the condensation drainage line ties into that bathroom sink. My ac was the first to go, all of the other units here are the original installs from 1991. And all of them have little 1/2" vent stacks in the pvc drainage lines before they run into the roof (and from there, apparently, across the ceiling, dropping down behind the vanity). When my new ac was installed, they replaced the drainline from the unit to the roof, with no venting. Is it even remotely possible that this has anything to do with the drainage issues in that sink? Or would that theory have been disproved by the fact that the line at the unit has been cut now and it is essentially an open pipe leading into the drain? I'm just trying to find a reason why a drain that hasn't been used in months except for ac runoff suddenly stops functioning, and hopefully increase my knowledge for future plumbing issues. Again, thank you for your time. Tami

Hi Tom, and thanks for your reply, I really appreciate it. I'm a new homeowner and I'm trying to figure out how things work. I'm sure this theory is probably insane, but if you have the time I'd love your feedback. The drain began backing up shortly after I had my rooftop ac unit replaced at the end of June. I have already determined that the condensation drainage line ties into that bathroom sink. My ac was the first to go, all of the other units here are the original installs from 1991. And all of them have little 1/2" vent stacks in the pvc drainage lines before they run into the roof (and from there, apparently, across the ceiling, dropping down behind the vanity). When my new ac was installed, they replaced the drainline from the unit to the roof, with no venting. Is it even remotely possible that this has anything to do with the drainage issues in that sink? Or would that theory have been disproved by the fact that the line at the unit has been cut now and it is essentially an open pipe leading into the drain? I'm just trying to find a reason why a drain that hasn't been used in months except for ac runoff suddenly stops functioning, and hopefully increase my knowledge for future plumbing issues. Again, thank you for your time. Tami

Hey Tami,

Let's get a few facts straight. Number one: the condensate line runs from the air handler in your unit and not from the compresser on your roof. The compresser's a sealed unit and produces no moisture. It's the cooling coils in the air handler that pull moisture from the air.
Since condensate runoff is just water it is highly unlikely this is what stopped up your lav. I fail to see where you hold any blame at all. You seem to forget you're on a shared drain with your neighbor.
Who knows what he's been putting down that drain. In the Tampa Bay Area we are forbidden to discharge sump pumps, rain water gutters or AC condensate lines into the drainage system. You said,"an hour later, warm coppery water came gushing out of the open branch on the drain, and with such force that it also filled up into the sink again"
This is when your neighbor drained his lav and it came up in yours.
Your plumber's missing the clog. He may have to open the wall up and snake from the vent. I hope you're not paying a plumber to do this. This is a common area and the cost should be picked up by the Condo Association. Good luck, Tom

Thank you for clarifying things for me, Tom. An association board member is saying it has to be my fault because my unit "has been occupied for about 13 years and no previous owner ever reported a plumbing problem of the kind she is experiencing", and the problem followed my ac install. But you hit the nail on the head, my neighbor has had houseguests using that bathroom for the last month while the only thing draining from my unit is ac runoff. Thank you again for your time, Tom, I appreciate it. Tami