Basement Toilet Drain Problems

[SOLVED] Final reply contains cause and solution.

Hello all, I am not versed in plumbing at all. So I am just going to dump all the info out here and someone experienced can decide what matters/is related and what is not. This downstairs bathroom that I will be referring to is something that was added well after the house was built (@ 1960). We did not build it though, it was like this when we bought it about 5 years ago.

The problem started about a week ago when I noticed water leaking out onto the floor underneath the basement toilet. We naturally thought it was the wax ring, and so we replaced it. The wax ring was in bad shape, almost nearly gone, and so we thought the problem was fixed. After putting everything back together though, the toilet was not draining properly. Thinking back I specifically remember seeing standing water in the pipe in the floor. I should have seen that as a red flag, but again this isn't my type of thing and after seeing the previous wax ring I wasn't thinking there was another problem. It was only after we put everything back together and the toilet was not draining that made me think of that. I have since snaked that drain for 25-30 ft. and couldn't find anything.

The problem in short is that the basement toilet only drains very slowly. I can flush without overflowing it but it does not empty the contents as the water level just slowly drops. If any of the two toilets upstairs gets flushed it gurgles the basement toilet and then sucks almost all of the water out of it. These are not directly above the basement toilet, about 10-15 ft. to the left of it which is the main sewer stack.

It seems to me that it would have to be a venting problem, as the only thing I can think of that would pull water out of that toilet is the vacuum created when the upstairs toilets are flushed pass by where the downstairs toilet drains into the main sewer line. It tries to pull air from there but if the vent for that line is blocked it tries to pull it from the toilet instead. This is where I need an experts help though, because it may seem like that is the only way but I really don't know enough about plumbing to know if that is actually true or not.

Another problem is though, that the sink right next to that toilet drains fine (more on this in a bit). Although I stated that this bathroom was added well after the house was built, the drain for the sink does seem quite old so I have no idea if it actually connects with the toilet drain. I would think so as the two drains are merely a couple of feet apart, but again I am clueless about this type of thing. This same sink had been having problems draining for a month now, and I thought the problems were related. However, earlier today I took off the p trap to try to do some snaking and in putting it all back together the pipe connecting the main drain to the p trap broke off it's lip. It was an older metal pipe and the lip just rusted and broke. I went and bought a PVC replacement though and after putting it back together, the sink no longer had any drainage problems while the toilet still did.

Also, I cannot find the vent for the basement bathroom. The sink and the toilet both drain directly into and then under the concrete, and there is no piping going into the wall at any point. I know it has to have a vent somewhere but I have no idea where it is. I know from going on the roof that there are three vent pipes - the main sewer vent which is the 3-4" one and two smaller 1 1/2-2" ones. One of the smaller vents is directly above the kitchen, so that one is obvious. The other small vent pipe though is within 10 ft. or so of the main sewer vent and because one of the upstairs bathrooms and more specifically the shower/tub in that bathroom is almost directly above the basement bathroom I have no idea if that other vent is for that shower/tub, the downstairs bathroom, or both.

Other issues include the basement floor drain overflows (not by a lot, it never overflows more than a few inches around the drain) when any appliance is drained and then drains slowly as well. This is also a new problem, and so almost surely related. It kind of bobs up and down as it drains, not dramatically but still noticeably. That drain is pretty close to where the bathroom drain is, but how the pipes are run under the concrete I have no idea, though I do know the toilet and sink drain are only maybe 10 feet or so away from this floor drain. I realize these drains are probably not directly connected but I thought maybe their proximity might matter.

I have no idea whether this next issue is connected or not but a while ago we started getting a really bad sewer smell in the house. It wasn't a constant smell, just once in a while - roughly once a week, maybe once every two weeks. The hall bathroom upstairs previously mentioned has two sinks and a shower/tub. They do not get used much so after reading up about it I thought maybe the p traps had evaporated and so I started running water through them periodically. That was about a month ago. It seems to have worked as that smell hasn't come back - yet. It has only been about a month so there is at least a chance it hasn't happened again, but I really don't think it ever went a month before where that smell didn't happen.

That is all of the info I have, and as I said some of it may not even be relevant but I thought someone more experienced should make that call. I appreciate anyone taking their time to read this post and help me solve the problem. I will run any kind of diagnostic that I can to help gather more information if it is needed, just let me know what you need. Again, I appreciate any help anyone can provide.

[EDIT #1] I realized that I did not specifically state that no other appliances are having any problems draining. Other than the ones I mentioned - sink next to the toilet in question was having problems draining but after replacing the s pipe/trap it does not, and the floor drain in the basement. Every other appliance drains normally.

I think I just had a breakthrough, but I want to run this idea by some more experienced people to make sure it makes sense. I originally thought that because the sink started backing up first that the clog originated in the sink and then slowly moved to where the toilet meets the drain at which point the toilet started having problems. At that point or shortly after it moved past where the drain meets the vent, creating an air gap which explained why when the upstairs toilets flushed it pulled air, or tried to, from the drain line.

In my above post I mentioned that after I replaced the s trap in that sink it ceased to have drainage problems. I forgot that I also snaked that the drain in between there too. That makes more sense than replacing the strap, since the s trap itself was not clogged. It was one of the smaller diameter snakes, and I am not experienced so I doubt I would have noticed if I hit a clog, moved that smaller diameter snake past it, and dislodged part of it without knowing it. I say part of it because like I said even though that sink drains fine now, the toilet still does not. So I am thinking that I must have dislodged just enough of it that the sink drain, being much smaller than the toilet, can now flow freely but the toilet still needs more room to drain properly.

It is too late now to go snake that drain again, so I will know for sure tomorrow after I do that. But I also wanted to post here and run it by someone more experienced to make sure my logic/assumption isn't faulty.

S trap? O you mean P-trap right? You said it’s a full bath right? Try running the shower and sink for a while and see if it backs up. I’d like to see some photos it might help us out.

like the above poster says run the fixtures ..if it comes in the shower...and its a true shower not a tub snake it thru the shower its a bigger drain than the sink and probably closer to the main....

[Picture links at the bottom of this post]

I never said that this was a full bathroom, the sink/tub that I mentioned was the upstairs bathroom. But this does have a shower, yes. However, as you can see from my pictures the previous owners cut some corners when doing this as the shower drain just juts out from the wall and empties directly over the basement floor drain. So I cannot use that auger from the shower, and running the water through there has no bearing on the drain from the toilet and sink.

I already mentioned that I tried running water through the sink, and previously it also backed up and drained slowly. It actually had problems first, roughly a month before the toilet became problematic. However, after replacing that pipe (sorry, I don't know the terminology and I thought it was called an s trap but obviously I was wrong but you should be able to tell what it is from my pictures) and using that auger through the toilet drain, the sink no longer backs up - just the toilet now. And I tested that sink drain thoroughly just to make sure it really wasn't backing up, I ran water through it for over 5 minutes. That is way longer than it ever took before it started backing up before.

Running any other fixture upstairs or down does not have any problems backing up or gurgling or anything else. Again, other than that draining water from anywhere does affect that basement floor drain. That basement floor drain acts almost exactly like the toilet - the water level raises a bit and then drains slowly. The only difference is that water does not get pulled dramatically from that basement floor drain when an upstairs toilet flushes.

My main curiosity is that water gets pulled from this basement toilet when an upstairs toilet is flushed. My reasoning suggests that the only way this could happen is if there is a clog in the basement bathrooms drain right where it meets its vent. So as the vacuum passes by where the basement bathroom drain meets the main sewer, it starts trying to draw air from the drain. The clog, because of the shape of the clog whatever it is, is preferentially blocking the vent and allows the slightest bit of wiggle room underneath the clog and continuing back up to where the toilet and sink drain is, sucking air through them. But again, I do not know plumbing that well and so I am not sure if there is any other way/reason that air could be getting pulled from that basement bathroom when an upstairs toilet flushes.

Toilet and sink with drain problems. I marked the wall where the room from the other pictures is, the one with the washer/dryer, the main sewer stack, the basement floor drain, etc... -

Sink drain showing which pipe actually got replaced. You can also see this pipe goes straight down under/into the concrete -

Shower from the downstairs bathroom with the toilet and sink that are having problems. This is where the drain that juts out from the wall directly over the floor drain in the other picture leads to. -

The main sewer stack, as well as many other drains that connect to it. I marked where both toilets tie into the main sewer stack and then there are also 3 sink drains from the upstairs bathroom close by that also drain into it. The white PVC pipe that is close by those same sink drains, is the kitchen drain and it goes to the other side of the house. I also marked the upstairs shower/tub drain (also a white PVC pipe, not to be confused with the other that I just mentioned) that sits almost directly above the basement bathroom in question. -

The basement floor drain, where you can see the drain from the basement bathroom shower just empties directly into it. I also marked the wall where the basement bathroom toilet and sink are. -

Again, I really appreciate the help and feedback. I am going to try and use that auger on the toilet drain again and see if I can't find anything. I will check back in a couple hours.

[EDIT #1] One other thing to note, is that because when the toilet flushes it raises the water level in the bowl would have to mean that it is either a) backed up or b) it cannot push the air ahead of it. Since the toilet bowl does drain, however slowly, I think that would rule out a blockage leaving only that it cannot move the air ahead of it. Or rather, that it cannot move it the air ahead of fast enough. Again, to me this would indicate a partial blockage right where the drain meets its vent. If the partial blockage was past the vent then the toilet should be able to empty fast but then at some point start draining slowly. But that is not what happens, because even if the toilet has not been flushed for quite a while it drains slowly as soon as you flush it. This behavior could mean that the blockage is in front of the vent, but then when the upstairs toilet gets flushed it would be able to pull air from the vent, rather than from my toilet or sink. So when put together, that should mean that there is a partial blockage right where the toilet/sink drain meets its vent.

So again, from someone more experienced - are my assumptions correct or is there something else that could be causing this behavior?

[EDIT #2] I made a crude diagram explaining what I think is going on. Thought it might help visualize the problem -

[EDIT #3] Unless I can actually find a vent for this, I no longer believe my diagram to be an accurate representation of the problem.

Sorry that I was not able to post back yesterday as we had a slight family emergency. I was able to use that auger again since then though, but to no avail. Sink still drains fine, but the toilet does not.

If I am right about the problem as depicted in my crude diagram from the above post, then I really need to find where the vent is. If anyone has any good ideas about where it might be after looking at my photos, I'd love to hear it. I am thinking it has to be in the walls there somewhere and I can see above those walls from that laundry room. I am going to try and stick an old smartphone through there using it as an impromptu camera to hopefully be able to find it.

Reading online though sometimes those vents are ran into the wall but only high enough so that it will technically work.. What are the chances that they might have only stuck it into one of those walls, yet didn't run it all the way to either the roof or to one of the other vent lines?

have you tried snaking thru the floor drain??????

Yes, that is the first thing I tried. That auger is 25-30 ft. and I could not hit/find anything, nor did it make any apparent difference in any of the drains (as opposed to when I snaked the toilet drain which allowed the sink to drain fine).

I believe that I did find the vent. I had to "eye it" but the apparent distance seems to put it between the sink and the toilet. Again, not being a plumber - does that sound correct? Does that make sense?

Another piece of info which may or may not help diagnose the issue is, that vent pipe is pretty old. And if you take a look at my sink pipes they also appear very old. I am thinking that the washer and dryer used to be where my bathroom is and then they moved it over to its current location and put the toilet and sink where the old washer was and the sink where an old utility sink was. This makes even more sense if you factor in that they took that shortcut with the shower drain. Why do that if they already had to break up the concrete to put in those drains? They could have added the shower later but that doesn't seem likely. Like I said, I have no idea if that helps diagnose the issue but more information is never a bad thing. I guess that information could help if there is a standard or normal way of venting a washer + utility sink? That could help me confirm where that vent is and the schematic of how those pipes might be run, both under the concrete and behind the walls.

Is there a trick a more experienced person could share with me about how to tell if you're using an auger and you hit a bend in the pipe as opposed to a blockage/partial blockage? Obviously a complete blockage would prevent the auger from moving forward without using noticeable force. But a partial blockage would be a bit trickier I would think? And that is the problem I am having - I can't tell if I am hitting a bend in the pipe or if I am possibly working the auger past a partial blockage. This is probably being made worse/harder by the fact the auger is probably only 1/4 the width of the pipe (assuming the drain pipe from the toilet is roughly 2"), instead of a bigger auger.

fill the floor drain until its level with the floor send the snake out until you run out of cable,when you clear the stoppage the water will drain away another place you can snake from is the toilet flange...you would need at least a 3/8" cable...don't fore it when you come to a restriction just stay there don't force it pull it back and push it forward without forcing it it just takes patience

Thank you Geofd, I really appreciate your feedback/input. After finding that vent I honestly think the blockage is between the toilet and sink, where the vent pipe meets that bathroom's drain pipe. Would your advice change any if I was to use that auger through the sink pipe that is coming out of the floor (disconnecting the p trap and the pipe that connects to it, going directly into the metal floor pipe - you can see an exact picture of what I mean in the links from the above post)? Same size cable? I think the one I have is 1/4" x 25 ft.

Scot777 said:

Thank you Geofd, I really appreciate your feedback/input. After finding that vent I honestly think the blockage is between the toilet and sink, where the vent pipe meets that bathroom's drain pipe. Would your advice change any if I was to use that auger through the sink pipe that is coming out of the floor (disconnecting the p trap and the pipe that connects to it, going directly into the metal floor pipe - you can see an exact picture of what I mean in the links from the above post)? Same size cable? I think the one I have is 1/4" x 25 ft.

Click to expand...

you wont do much with that cable once it hits the 4" but if yo have the time that's the size you would use on the sink at least that way your gonna have a clean sink drain... you could cut into the vent and snake it from there you want to be as close to the main as possible

Well, I have had no more luck using that auger. I have since found out that what I thought was the bathroom vent pipe is not, and I have looked everywhere above that ceiling and I cannot find a vent pipe anywhere.

If I am right about the pipes from that bathroom having been there since the house was built and not put in when that bathroom was built, then how do you think they would have vented that? It has to be under the concrete somewhere because there are no pipes ran into the walls anywhere above the concrete. Even if it is branched off the drain pipe under the concrete somewhere I cannot find any pipe going upstairs anywhere.

Is there any possibility that the bathroom drain ties into that floor drain? Either directly as a drain pipe or as a vent pipe only?

not sure were you are snaking from but if you have no luck with the floor drain use the toilet flange …

Not having any luck snaking from anywhere.

But the situation just got weirder.

In an attempt to locate the vent for the downstairs bathroom I went investigating the rest of the plumbing in order to see how it was ran and where the other venting might be. The original cast iron (or whatever metal it is made from) has been replaced with PVC. Some of the previous piping has been removed but a lot of it still remains. In places under some of the sinks you can see the old metal pipes with caps on them.

Stay with me here because I know what I am about to say sounds crazy but I swear I am just describing what I see - I cannot find a single vent for any of the drains, other than the main sewer stack that vents out the roof. I can see the drains upstairs go directly into the floor. I then go down into the basement and I can see those same pipes coming directly from the floor, and the proceed directly to the main sewer stack with no other branches anywhere.

Since there is water in all those sinks' p traps, there is some mechanism somewhere allowing either the air to vent or allowing the air to be moved around the water. I also do not see any air admittance valves so I think that rules out the former. Is it possible to do the latter by emptying the p traps into a larger diameter drain and sloping it down, thereby creating enough room for the air to move around the water instead of forcing it out?

Is what I am describing even possible or do I have to be missing something, somewhere, somehow?

In the below picture on the left you can see the new PVC piping, some white and some black that both go into the main sewer stack. To the left/under the white PVC on the left, you can see a silver metal pipe which is part of the old metal drain pipes. The pipes going up to the bathroom sinks is still there but capped off underneath said sinks. You can also see a cap on the end of the same silver metal pipe, which used to go to the kitchen (which is where the new white PVC pipe goes now).

In the same below picture but on the right hand side you can see a white PVC pipe. This is the new PVC pipe that goes into the upstairs hallways bathroom's tub and shower. There is another silver metal pipe sticking out from close to the main sewer stack that is also capped off on the end, this is used to be the old shower and tub drain. I believe one of the smaller roof vents is connected to the old piping that is above this floor and still sitting behind the wall of that same shower/rub.



I am going to link another picture showing the kitchen drains (one normal, one from the garbage disposal), which are on the opposite side of the house. Again you can see the old capped off metal pipes. I believe one of the vents on the roof connects to this old piping because the newer white PVC pipes go directly into the floor and then continue directly to the sewer stack on the other side of the house. I can follow that pipe every step of the way and see all of it, nothing branches off of it anywhere. There is however part of the old metal piping that goes down and behind the wall.



I have plenty more pictures I can share if anyone wants to see more or if anyone needs to see a specific part of the system. I am also more than happy to go take more pictures grabbing whatever details you may need to understand what is actually going on.

After bouncing some ideas off of other people I may have a better theory on what is happening. Going to throw it out there and see if it makes sense to others as well.

The main sewer out could be clogged as originally thought, which explains why the floor drain backs up. If that is the case then when an upstairs toilet flushes there will inevitably be an air gap between where the main is currently backed up to and the air being pushed forward from the vacuum created by an upstairs toilet flush. Because those two toilets are upstairs, the gravity force of the flush is hitting that air gap, and compressing that air gap and the toilet drain must be sitting right inside of that air gap - and that is what is pulling air from my toilet, NOT the flush passing by the toilet drain and pulling air in behind it.

Just wanted to post a final reply in case anyone else ever comes across something like this. After concluding that it was reasonable to be a main line clog we scheduled a plumber to come by since augering a main line is way beyond my experience and I'd very likely do more harm than good if I tried.

They did say that yes it was a main line clog, and his best guess as to why, due to excessive sludge near the clean out, is that it was sludge build up. When I asked why it caused the water and air to be pulled from my toilet, he said he is not quite sure. He said he has seen it before and he thinks it is likely that it has something to do with when the main line gets clogged just the force of that water pulls on it. So it was at close to that final conclusion my buddy helped me come up with, not necessarily the air gap compression but the force of an upstairs flush pushing on that clog.

So to anyone who may come across this in the future, just because water/air is being pulled from a fixture it does not necessarily mean that it is a venting issue. Obviously this would apply moreso to any fixtures that are close to the main line. If your fixture is higher up in the house, or far farther away from the main line then it is still most likely a venting issue. Still, my main point is that water and air being pulled does not 100% mean a venting issue.

[EDIT] Can anyone tell me how to edit my title so that I can put a [SOLVED] tag on it to help any people in the future who come across this?