Why does a toilet "burp"?

[GL77]

I have a Kohler Rialto that is working fine. I just wonder why, every so often, maybe once a month, I will go into the bathroom to wash my hands or put something away and I'll hear what sounds like a bubble come up in the toilet, just randomly. I've never been able to look over fast enough to see a bubble so I don't know if it is coming from the bowl or the tank. Is there something I should check or is it nothing to worry about? I live in a small house, 1 bathroom, plumbing is about 15 yrs old, pvc DWV, all the drains are working fine. Just curious.

 

[LLigetfa]

It is not normal but being such a rare event, it would be hard to find the source.

 

[Sponsor]

 

[GL77]

Are there any developments I should keep an eye out for? My biggest worry would be a leak at the base but there is no sign of leaking.

 

[Tuttles Revenge]

It is Not normal for a toilet or any plumbing fixture to Burp. When I was briefly doing drain cleaning service, a toilet might burp when the main drain was full of water and water was going down another drain where the vent for the toilet was full of water. The water from the other fixture added pressure to the water in the drain/vent for the toilet and the pressure pushed against the water in the toilet trap. Generally I would notice that the water level would drop in this scenario as a clear indicator of a full / backed up main drain.

 

[LLigetfa]

Some water conditioning systems add air into the water stream that sometimes accumulates in the piping until it moves forward. Some water sources can have air or gas entrained.

 

[GL77]

Finally heard it again yesterday when I was putting stuff away in the bathroom. Sounded like a big bubble came up but when I looked over I couldn't see anything. Nothing was running at the time at all, no water, no drains. What the heck.

 

[Jadnashua]

Was it windy out?

 

[Jeff H Young]

wind might be a consideration heavy wind other wise approx 100 percent of time its some sort of stoppage ,totally abnormal to have this happen . but happens regularly with a stoppage

 

[GL77]

Thanks, guys. I don't think it was particularly windy that day. I will pay attention to that the next time.

 

[Tuttles Revenge]

IMO wind is the least likely cause. Try to blow bubbles through a straw 4 inches deep and see how much pressure it takes to create that bubble.. could wind do that?

Main line clog with the drain and AAV vent on the horizontal is the more likely scenario. Or something that approximates that.

 

[Jeff H Young]

yep just about 100 percent of time its a blockage or it was just built wrong

 

[Reach4]

Septic tank or sewer-- you did not say. So probably sewer... but I thought I would check.

 

[Jeff H Young]

Either one septic or sewer get plugged drain slow etc.

 

[Reach4]

either one septic or sewer get plugged drain slow etc.

Septic would have more urgency IMO, and the OP may not have been thinking along those lines.

 

[Clarice8419]

It is not normal, but it is such a rare occurrence, tracing the source would be difficult.

 

[GL77]

I'm on city sewer but I have a sewage basin in the yard that pumps uphill to the city sewer. I had a plumber out for something unrelated the other day and he said, being as all the drains are functioning normal and it happens really infrequently, it could be caused by the city sewer sucking air through my vent stack.

 

[Tuttles Revenge]

I'm on city sewer but I have a sewage basin in the yard that pumps uphill to the city sewer. I had a plumber out for something unrelated the other day and he said, being as all the drains are functioning normal and it happens really infrequently, it could be caused by the city sewer sucking air through my vent stack.

Your entire house or a portion of it connect to the sewage ejector? Does the toilet in question drain to the basin or is it on an upper floor. I suspect that if its draining to the sewage ejector basin, that the basin itself might not be vented and when it discharges its drawing air from the house system. Or Burping might be caused by waste entering the sump basin and needing to displace air through the house venting system causing a tad bit of positive pressure for a minute that is expelled at the toilet trap.

 

[GL77]

Your entire house or a portion of it connect to the sewage ejector? Does the toilet in question drain to the basin or is it on an upper floor. I suspect that if its draining to the sewage ejector basin, that the basin itself might not be vented and when it discharges its drawing air from the house system. Or Burping might be caused by waste entering the sump basin and needing to displace air through the house venting system causing a tad bit of positive pressure for a minute that is expelled at the toilet trap.

This is a large concrete basin buried in the yard, I suspect a repurposed septic tank, with a lift pump, that my plumbing drops into. I live in a very small home, 1 story: 1 bath, kitchen sink, dishwasher and laundry. The burping has happened when no water is running anywhere but I guess it is possible that the sewage pump had been running from something having drained prior, although that pump empties the tank very fast. The basin itself is not vented separately from the house vent. I think you have something there and I'm going to keep track of whether I had previously been draining water before it happens. Thanks.

Edit to add: yes, the whole house empties into the sewage basin, from which it is pumped uphill to the city sewer.

 

[Reach4]

Note the normal level of the water in that toilet. After a burp, compare the new level to the normal. Pretty much the same?

I am wondering if the burp is outward, as bacteria outgassing while the venting is some how blocked. If the action is due to the grinder pump going on, and the venting was not right, there would be a vacuum rather than an outgassing. I would expect the level in the toilet to drop a bit.

I am not sure what my action item would be. My first thought was to rod the line to the tank, because that is cheaper than camera inspection. Camera inspection could diagnose more conditions.

 

[GL77]

Reach4, you are right, it is more of a bubble coming up, and it doesn't change the level of the water that I can see. I can open the tank lid outside and observe the drain working so I don't think there is a clog but when the weather warms up I may take a closer look. It's probably only 10 or 15 feet between the toilet entering the main drain and the main drain terminating into the tank.