Sewer gas coming up through toilet bowl itself

[Tripp Knightly]

(This isn’t just toilet related, so posting here.)

I’m half expecting some of you to tell me I’m nuts but I’ll tell you anyway. I have a downstairs (ground level) toilet. If I close the seat cover say overnight and open it: pronounced sewer gas. If somebody right above upstairs showers (drain uses same vent stack): sewer gas. The stink really is in the bowl not at the base of toilet, dispelling I think a wax ring / flange issue. The toilet feels solidly mounted and the problem has emerged in the last year or so only; plumber install ~ 5 yrs ago. Proximate p-traps are all primed, in fact all p-traps are (all drains in use). Sometimes it seems like the American Standard 1.28 gpf toilet doesn’t flush well on the low vol flush.

So I’m wondering: can sewer gas permeate straight into the bowl through the water- it’s not like I see bubbles but maybe it won’t work that way. I have an HD endoscope so I can rig up something to look at the vent stack from the roof.

 

[Reach4]

Does the bowl refill fill enough? Ideally, after a flush, it will fill to the level that the bowl will hold for five minutes after you slowly pour an extra quart into the bowl.

There can also be stuff growing in the toilet passages.

Septic or sewer?

 

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[Tripp Knightly]

Does the bowl refill fill enough? Ideally, after a flush, it will fill to the level that the bowl will hold for five minutes after you slowly pour an extra quart into the bowl.

There can also be stuff growing in the toilet passages.

Septic or sewer?

Refills and holds ok. Sewer. In a heavy wind I will see SOME motion on the bowl water surface but never have I seen a siphon where the level drops say 3” to the gurgle point.

 

[Reach4]

I would consider pouring some bleach down the overflow tube with a funnel.

There are some devices that inject a bit of chlorine down the overflow tube with each flush.
The Fluidmaster Flush n Sparkle, and Kaboom Scrub Free bleach cleaners are good, because they go in series with the bowl-refill tube and dump the chemical down the overflow to the bowl. The Kaboom can be reloaded, not only from the product they sell, with a slow-dissolve swimming pool or spa chlorine or bromine product. They put no chemical into the tank water.

The downside is that they pass the refill water through the gadget and more tubing. So it is possible that they could reduce the refill. If you used a fill valve with an adjustable refill rate, you may be able to compensate.

The downside of using a chlorine puck that puts chlorine into the tank is that chlorine is harmful to your flush valve rubber over time. A short exposure is not significant. Some think that the reduced life of the flapper is worth it.

 

[Reach4]

My thoughts above were along the lines of stuff growing in the toilet.

If somebody right above upstairs showers (drain uses same vent stack): sewer gas.

OK, I did not give that sufficient attention. That would imply a blockage that puts the path to the real vent under water. This could be due to a partial blockage, but it could also be due to a belly (big sag) in the line.

An AAV does not help a toilet from getting gas pushed in. So there needs to be a path to the roof vent, even if it is a fairly long path. A block or belly can block that path, at least temporarily.

I have a suggestion for you if you are motivated enough. You can make an open-tube manometer with some cheap clear tubing and a glass jar or glass glass. That would read the water pressure on the other side of the water seal. It is not that hard once you get over the idea of threading a tube through your toilet trap. The tube could maybe instead be thrust through the drain and trap of the adjacent lavatory.

You can measure the air pressure at the far end of the tube. The procedure would be to run some clear tubing through a trap into the trap arm or past the weir in a toilet. Blow to remove any water in the tube.

Take the near end, and put it into a glass of water. This glass could be elevated, maybe somehow taped into the soap dish. It could be low for better positioning for video. Tape the tubing to support that to keep the end of the tubing in place. If vented, the level of the water in the tubing should be about the same as the other water in the glass. If there is vacuum in the drain air, the water level in the tubing would drop relative to the level of the water in the jar.

Clear tubing is pretty inexpensive . If you know somebody on oxygen that person probably throws away suitable tubing every month.
You can thread the tube through a lavatory trap, if there is nothing blocking the way. You can shove the tubing through the trap of a toilet. Through the toilet would directly show what the toilet is faced with.

There is an electronic manometer that could be used. However the open-tube manometer does not need calibration. The electronic one might be able to remember peaks however -- I never used one.

So what do you do with the info? If there is pressure recorded of more than 1 inch of water during that shower, that could explain the symptom. Why the venting is not sufficient to prevent a 1 inch pressure would could be investigated.

This picture tries to show a belly, similar to what you may have:

 

[Tripp Knightly]

My thoughts above were along the lines of stuff growing in the toilet.
OK, I did not give that sufficient attention. That would imply a blockage that puts the path to the real vent under water. This could be due to a partial blockage, but it could also be due to a belly (big sag) in the line.

An AAV does not help a toilet from getting gas pushed in. So there needs to be a path to the roof vent, even if it is a fairly long path. A block or belly can block that path, at least temporarily.

I have a suggestion for you if you are motivated enough. You can make an open-tube manometer with some cheap clear tubing and a glass jar or glass glass. That would read the water pressure on the other side of the water seal. It is not that hard once you get over the idea of threading a tube through your toilet trap. The tube could maybe instead be thrust through the drain and trap of the adjacent lavatory.

You can measure the air pressure at the far end of the tube. The procedure would be to run some clear tubing through a trap into the trap arm or past the weir in a toilet. Blow to remove any water in the tube.

Take the near end, and put it into a glass of water. This glass could be elevated, maybe somehow taped into the soap dish. It could be low for better positioning for video. Tape the tubing to support that to keep the end of the tubing in place. If vented, the level of the water in the tubing should be about the same as the other water in the glass. If there is vacuum in the drain air, the water level in the tubing would drop relative to the level of the water in the jar.

Clear tubing is pretty inexpensive . If you know somebody on oxygen that person probably throws away suitable tubing every month.
You can thread the tube through a lavatory trap, if there is nothing blocking the way. You can shove the tubing through the trap of a toilet. Through the toilet would directly show what the toilet is faced with.

There is an electronic manometer that could be used. However the open-tube manometer does not need calibration. The electronic one might be able to remember peaks however -- I never used one.

So what do you do with the info? If there is pressure recorded of more than 1 inch of water during that shower, that could explain the symptom. Why the venting is not sufficient to prevent a 1 inch pressure would could be investigated.

Thx for all the detail and I think I follow. I happen to have such tubing because I’m a pack rat and will keep things that I might use once in the next quarter century.

One question re: If there is vacuum in the drain air, the water level in the tubing would drop relative to the level of the water in the jar. Wouldn’t the siphoning cause the jar level to go down and more water into tube?

 

[Reach4]

One question re: If there is vacuum in the drain air, the water level in the tubing would drop relative to the level of the water in the jar. Wouldn’t the siphoning cause the jar level to go down and more water into tube?

The tubing would contain all air, except for the end that is thrust into the glass of water. So if air pressure in the pipes is the same as atmospheric pressure, the level in the glass and the level in the tube match. If the level in the tube is 1 inch lower during the shower, then there is pressure. If 1 inch higher during that shower, a vacuum. But since the middle of tube goes higher than 3 inches above the level of water in the glass, a siphon cannot start.

 

[Tripp Knightly]

The tubing would contain all air, except for the end that is thrust into the glass of water. So if air pressure in the pipes is the same as atmospheric pressure, the level in the glass and the level in the tube match. If the level in the tube is 1 inch lower during the shower, then there is pressure. If 1 inch higher during that shower, a vacuum. But since the middle of tube goes higher than 3 inches above the level of water in the glass, a siphon cannot start.

Got it. I thought we were looking for siphoning evidence that water seal was breaking as opposed to gas muscling its way into the bowl (same gas result either way I assume).