Another plumbing mystery.

[N80]

I live in a 30 year old house on a septic tank and just started having a strange problem when I flush the upstairs toilet. As the flush is almost complete, even after the flapper has closed I get a deep, gurgling, drumming noise that comes from the shower drain. It lasts for several seconds and it is loud. If I hold my hand tightly over the shower drain I can feel a push of air pressure when this noise starts. The toilet, which is an old high flow, flushes and drains perfectly. The shower, also high flow, and sink drain perfectly. The other upstairs toilet drains fine and causes no noises. I'm stumped. Any ideas?

 

[EddieWalker]

Sounds like your vent is plugged up and the drain from the shower is acting like a vent, but because there is a trap under it, it's pulling the water in the trap. When the toilet flushes, it fills the pipe with a lot of water real fast, so the trap is critical on toilets. More then any other trap. All that water creates a seal in the pipe and it will pull air from behind it to allow it to flow. If your trap is plugged, then it's going to pull air from whatever else is behind it. In your case, it sounds like the shower drain is where it's getting the air, after it pulls the water out of your trap. I wonder if you can smell sewage from the shower after this happens? Of course, there might still be enough water in the trap to keep out the gases from your tank, and some tanks don't smell as bad as others.

Look at your vent, maybe send a hose down it and turn it on to flush out what's in there. Or run a snake down it to see if there is anything in there.

Good luck,
Eddie

 

[MossRoad]

Your vent stack is probably plugged.
​

 

[MossRoad]

Ha! Eddie beat me to it! :thumbsup:

 

[N80]

I thought of that too but it is pushing air out of the shower drain, not pulling it in. And when the vent stack in my cabin was clogged the toilet would not flush completely. This toilet is flushing great. And, when I sealed the shower drain with my hand it still flushed fine and still made the noise. There has been no odor, even sniffing the shower drain.

Anyway, the vent stack was my first thought, that's why I tried flushing with the shower drain sealed. However, I will still check it.....I have a snake.....or I'll get someone else to, I hate going on the roof of my house. I'm a chicken when it comes to heights and it is steep and way up there.

Just out of curiosity, what would block a vent stack up on a two story house.......?

Come to think of it there were tons of fireworks the night of the fourth....what are the odds on that?

 

[rekees4300]

Just out of curiosity, what would block a vent stack up on a two story house.......?

Could be a wasp nest.

 

[N80]

Me on the roof with a wasp nest......I'm envisioning a Chevy Chase or Three Stooges sort of moment....

 

[Pops15]

If it's pushing air out of the shower drain it could be a plugged or nearly plugged drain.

 

[Transit]

I am thinking maybe a bird got into the vent stack. One of the functions of the vent stack is to break the vacuum caused by the falling water in the waste pipe. If the vent stack is plugged, than air will be drawn in elsewhere, the shower drain.
You could try blocking the shower drain and other drains and giving all the toilets a good flush pulling whatever is in the stack along.
:thumbsup:

 

[Egon]

Hmm, got a friend with exactly the same problem. he checked his vent. It was clear. Dug up his septic line. it was clear too. He still has the gurgle.

 

[chipsndust]

Wasps, birds, leaves, mice, squirrels.

Lots of things can plug the roof vent.

 

[N80]

Are any of those things likely to plug a roof vent? I've never seen it happen in any home I've ever lived in. But, we've got all four of those things including tall trees over the house. Could even be a pine cone I guess.

I suppose once the item is detected the next decision is whether or nor it needs to come up or go down.

 

[Pops15]

Are any of those things likely to plug a roof vent? I've never seen it happen in any home I've ever lived in. But, we've got all four of those things including tall trees over the house. Could even be a pine cone I guess.

I suppose once the item is detected the next decision is whether or nor it needs to come up or go down.

Highly unlikely, plus you said its pushing air out the shower. Forget about the vent. Your main sewer line is about plugged up. Ask me how I know.

 

[Transit]

Plugged main line, possable. But no reported issues with flushing the other toilets.

I have had birds get into my house down the chimney and come out the gas hot water vent, caped the chimney. :confused2:

 

[N80]

Highly unlikely, plus you said its pushing air out the shower. Forget about the vent. Your main sewer line is about plugged up. Ask me how I know.

We've got 4 people living here. All toilets, sinks, tubs, showers and dishwasher draining fine. And the main sewer line is probably only 20 feet long as the septic tank is right out the back door. I'd surely prefer a bird in the vent stack to a clogged main line so I hope that isn't what it is.

 

[Egon]

Have you looked into the septic tank?

 

[N80]

No! I'm afraid there might be a troll in there making that gurgling noise! Its as good a theory as any so far.

 

[MossRoad]

I found in my house (which we bought used and are therefore not responsible for the way it was constructed, modified, massacred, etc... ) that the straps holding the vent stack vertical through the wall and up,out the roof did not hold the vent stack for the bathroom and it slipped down 6" into the basement. That, in effect, made a trap at the bottom of the vent where water would gather. In the winter, that water froze and when we flushed the toilet, the bathtub drain would gurgle. That's how I knew something was wrong. So I followed the drain pipes in the basement and found the sagging vent stack, which is supposed to be higher than anything else in the line. I made two brackets on the corresponding joists and ran a 2x4 under the sagging vent stack. Then I used threaded rods with nuts and large washers through the brackets and 2x4 and started jacking it up a few turns at a time until I got it at the proper level. That stopped the gurgling in the bathtub. Now I just have to permanently fasten that 2x4 to the joists and remove those threaded rods that I keep bonking my head on! :laughing:

 

[Pops15]

We've got 4 people living here. All toilets, sinks, tubs, showers and dishwasher draining fine. And the main sewer line is probably only 20 feet long as the septic tank is right out the back door. I'd surely prefer a bird in the vent stack to a clogged main line so I hope that isn't what it is.

I had the exact same gurgling noise and air coming out the tub drain. Everything appeared to be draining fine. My first thought was a problem with the vent. I and a garden hose down the vent and flushed it out really well. The gurgling persisted. The gurgling got worse over the next few days. I knew it wasn't the vent so I pulled the inlet cover off the septic and had my wife flush a bunch of toilet paper.......I saw water entering the tank but no paper. We repeated the test with the same results. I knew the main sewer line was partially plugged. Water could still get through but we had 12+ feet that was full of paper and solids. I just backfed the garden hose in the sewer to loosen the blockage and drained a tub full of hot water to flush it out. Had this problem 3 times in 29 years so your problem sounds very familiar.

 

[N80]

Hmmm. Sounds like I need to make a trip under the house. I sure hope there is an access stub to the the main sewage line.

I still wonder why the shower in the kids bathroom doesn't gurgle when their toilet is flushed?