Bizzar plumbing issue.

We live in a country house that was built by the owner 25 years ago. There are some gnarly things in this house that I think pros would not let happen. I suspect our freakish plumbing situation may be caused by this type of thing.

Every once in a blue moon, bubbles start comming up the toilet. Then we hear a gurgling sound in all of the drains in that bathroom and the toilet flushes itself. Water then poors out onto the first floor through one of our recessed light cans.

The first time this happened we called the plumber, and stuck a camera down the pipe and couldn’t find anything. The toilet worked fine and everything went back to normal. We’ve lived here four years and this has happened three times.

Flushes itself?

Or just empties itself. I can see it emptying out but I can’t figure out how it would flush.

Usually bubbling signifies a back pressure problem which means that the venting on the plumbing system is blocked.

Without a vent the water sits in the full length of the drain pipe instead of continuing to the sewer system or cistern. Then gasses will push the water backwards.

Sticking a camera down the drainpipe wouldn’t tell you much as the drain pipe would probably be working just fine. The vent to that pipe however, might be blocked.

bubbles in the toilet are the drainage system alligators, they are laying in wait and about to bite whatever is on the toilets. arm yourself.

when water goes down the drain then air has to escape somewhere, ideally through the vent system out the roof, if the vent is blocked (or the system nonfunctioning for some other reason) then the drains won’t drain or will be slow or the air finds another path. this might be the bubbles. the toilet can flush itself when the water gets sucked in by a bad vent system acting on another drain.

water constantly pouring out a light fixture would be a leak in the water supply. water coming out when draining a sink, toilet or tub is a drainage leak; these will be following and linger after the draining.

That sounds right. Where should there be venting on the plumbing system? I wouldn’t be suprised if there wasn’t any installed, or installed adequately. Is this an easy fix?

We have a septic tank if that matters.

If the water backs up to the point it is blocking the vent you will also get bubbles, sounds like a slow drain to me.

I suspect the pressure is temporarily breaking a seal and when the pressure equalizes the seal tightens back. It could be the toilet gasket.

Is the light located under the bathroom wall? I’d be concerned about mold behind that wall.

near every drain, as it goes into the house drainage system, there is a vent pipe. it is a parallel path in the drain system at those points to allow air to escape. the vent system then travels at some high point and out the roof. debris, leaves, animal nests, dead animals can get into the pipe and restrict the air flow.

It drains quickly. I suspect there is some mold, but as long as I don’t have health issues, it’s innocuous. We’ve been through this before.

I’ll have to look into where the vent is and see if I can do anything.

I would be more worried about the fact that this might be POOPY TOILET WATER leaking through your ceiling! Or am I misunderstanding, and the leak is not connected to the toilet?

Your septic tank needs to be drained.

septic tanks need the exit filter (if there) cleaned once or twice a year. and the solids pumped out every three or so years.

if the septic tank didn’t drain you would have a stinky puddle where the tank is. and water would not drain at all in your house.

Google Image for “plumbing vent” and you’ll see lots of diagrams of how plumbing stacks should be laid out…

Is the light fixture below the bathroom? Or is this a 1-storey cottage?

Toilet flushes itself is something sucking the water down the pipe. Usually, this is due to a slug or rush of water down the drain and no ventilation, sucking everything in its path along with it.

As others said - bubbles? sounds like very poor drainage.

A possibility is that the is a stretch of pipe that is horizontal but actually slopes the wrong way a bit, so where it should drain and vent, it is creating a plug like a U-shaped trap does, instead of allowing venting.

If it is 1 storey, then maybe what is happening is back pressure (air buildup in septic tank?) forces drain water out the vent stack, and previous owner left the vent stack to vent in the attic rather than through the roof.

I sure hope it’s clean water, not sewage!

Best thing you could do is try to make a plan of exactly how the drain system is laid out. If the light fixture is from the attic, crawl around the attic and figure out what pipes are there.

You should have a vent going up from every collection of drains - one or more for the bathroom, one for the kitchen sink (unless it backs onto the bathroom and shares it) one for the laundry tub and washer drain, etc. These should obviously be poking through the roof into the sunshine.

I sure hope the guy did not leave a vent stack ready to continue up, a foot or so above the floor line, then walled it in forgetting to extend it to the roof. Does the house sometimes smell like swamp gas?

To elaborate, because I was in a rush to leave work:

The bubbles are septic gas backflowing through your house drains. This will add enough energy to drain the toilet down below the bowl trap, and you could get gas venting into the house.

Happened at my previous house in NC. $200 to pump out and inspect the tank, and it was good.

And the septic gas would dissipate if the plumbing were properly vented.

Depending on the code in effect when the tank was installed, it can be perfectly valid to not have a vent. My house and tank were built in the mid 50s and no vent exists. Whoever buys the place next may well put one in; I considered doing it myself.

FWIW, once the tank was pumped, the gas problem went away.

I’m guessing that this is exactly what happened, and the stub is located above the recessed can light

I like this. This house has had severe settling, and I’ve noticed more shifting recently. I think the drought has something to do with it.

My guess is both.
If this was a home-made construction, then he may have had a friend or really cheap plumber come in to to the rough-in before he even had the walls - or celing trusses up. the guy would ahve done plumbing up to the sink level and left it for the home builder to do the rest.

You should be able to trace from the toilet to where it joins a drain (and piece goes up) with the camera. You know, “curved Tee joint 2 feet from toilet trap”, etc. If that piece it’s joined to does not have a corresponding 3-inch or better pipe popping into the attic and up through the roof, you got some drywll chopping to do.

If your drywall skills are good, it would not hurt to cut a few squares (if you can, on the wall on the other side of the toilet) just to see where it all goes if you find a problem.

Yeah, if you have, say, a 10-foot slug of water in a pipe no longer angled downhill, that could get some serous momentum when pushed by a nice powerful bubble.

A septic tank may not need a vent itself if it does vent through the house vents - but if the house vent is not good, or the run to the tank from the basement is now uphill, you do not vent until the buildup forces the bubble to push out obstructing water.

If your drains bubble on their own then odds are it’s a side effect of unvented gas pushing out from the tank. (Sometimes, unlike in life, shit does not run downhill)

Another possibility is poor design of “wet venting” where what’s supposed to be a dry vent stack is used as drain by other, up-pipe plumbing like sinks or upstairs fixtures. This means that drain from “A” could back up and flow out “B”.

Or, when the house settled, one of the horizontal lengths of soil stacks cracked or developed a leak at the top. Which might only manifest when the pipe was full during a backup situation.