Leak in basement when toilet flushes or shower runs


Old 12-28-08, 03:49 PM
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Leak in basement when toilet flushes or shower runs

Hi, all.

New to the forums. My wife and I just bought our first house. It's a Colonial twin built around 1920. We only have one bathroom on the second floor. As of this morning, whenever we flush the toilet or use the shower, we get a really good amount of water in the basement, right by the cast iron pipe comes straight to the basement.

I cut away a piece of the subfloor to see if I could get to the leak, but it looks to be higher. I can't see where it's coming from, though.

I suppose my question is twofold ... Is this something I might be able to fix, and what's the best way to locate the leak? Is it possible to do so without opening up the wall?

I'm guessing I'll need to call the plumber, realistically. I'm pretty handy, but I think this might be out of my reach. Is this a huge (read: expensive) job for the plumber? I'm a bit nervous as the house is a rehab and everything is brand new. I'd hate to start ripping out drywall.

Thanks for any help!
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Old 12-28-08, 05:47 PM
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Hi Bill, I'm not a plumber, but while you are waiting for one to jump in, I thought I would add my thoughts. Being a rehab, with cast iron into the basement, I would take a look at what the vent at the roof is made of. If plastic, then they reworked some of the drain lines and there is possibly a rubber sleeve on that cast iron pipe to make the change from iron to PVC. If they didn't clean up that iron really good, that's where the leak could be. Finding that or the real leak is probably going to take a plumber and besides, they have those long thin inspection cameras to avoid tearing out all of the walls. Let's see what the board has to suggest.

Good Luck,
Old 12-28-08, 06:17 PM
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Thanks, Bud.

The vent is cast iron. Just went to double check. We moved in around Thanksgiving, and the leak just started yesterday.

I'm hoping it's fixable! Or at least low enough to avoid having to rip out the brand new cabinets in the kitchen that would likely block access. Ugh.
Old 12-28-08, 06:49 PM
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Also, it may be worth mentioning that it's leaking a LOT of water. This morning I mopped up and nearly filled a five gallon bucket. It seemed strange that it would happen that much that quickly, considering there was no leak up to that point.
Old 12-29-08, 04:09 AM
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I'm no expert, but it seems to me that you're going to have to find the source of the leak.

If I'm reading you correctly, your house only has one bath and it's on the second floor? If so, why does the vent go all the way to the basement and while I'm at it, do you have visible signs of a leak, if you run water anywhere else in the house?

The vent is supposed to breathe, it isn't supposed to carry water. Ordinarily, there's a vent attached to the toilet plumbing and if there's a backup downstream, water could backup into the vent, but I'm at a loss as to why the vent goes "below" the only toilet to the basement.

The vents are also not supposed to leak, but if you have a fairly new clog and a leaky vent pipe, then theoretically you could have what seems like a new leak. (If the house sat vacant for a while, the drains could've dried and when you moved-in, you filled the clogged, empty outflow with slow-draining waste)

Another possibility is that there's a leak somewhere and it's just following the chase down as the route of least resistance, but then you'd probably have signs of a leak elsewhere, especially if the leak is on the second floor.

Again, there really isn't a lot that could be prescribed until you find the hole. If it's in the vent and if there's a clog causing backup, then you might be able to stem the flow, but that's not going to fix the leak.

As for how to find it without seeing signs elsewhere or tearing-up too many walls/floors, it seems the best option would be Bud's suggestion of getting a plumber with a camera to come by for diagnostics. Of course they will charge for this service and they will try to sell you a repair, but without knowing the design of your house, there's not a lot that I can think of from afar and it may cheaper than the alternative.

(Though, I guess you could pull up the toilet, take a shower and see what happens in the pipe, but that's not going to help you find the leak, it'd just show whether or not you have a clog. The same might also be surmised, if you hear the toilet or bathroom sink "burp" during a shower and that wouldn't involve actually pulling what sounds like your only toilet)

PS) I'm not sure how or where the water is puddling, but if it's going to be a couple of days, you might want to invest in a Shop-Vac and if it's going to be a week or more, you might want to consider temporarily draining your shower elsewhere, if that's an easy option.

Last edited by TryAgain; 12-29-08 at 04:29 AM.
Old 12-29-08, 05:00 PM
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First of all, are you on a septic system or a town sewer line?

I am thinking a possible back-up is causing the leak. Quite often the toilet is very close to the 4" cast iron stack, and if the line were to back up someplace, it could run right down the stack.

Does everything seem to drain properly?

If everything is draining fine and you do not think this is a plugged drain problem, then we need to look at the possibility of a broken or cracked pipe in a wall. This is quite common in old cast iron pipes. But it could also be a joint that is leaking. Or the leak could just be coming from the wax seal on the toilet, which could also lead us back to a patrially plugged drain.

I think the best thing to do is to do as much research as possible and then call a licensed professional.

Also remember, water flows downhill, unless it is a pressure leak, so start at the bottom and look up.

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