Sewer gas

Sewer gas implies you are on some sort of community sewer system and not an individual septic tank. Am I right?

Yes.

I had a similar problem. I finally called the plumber and he cleaned out the drain in the shower. It seems that some kind of mold had been growing in it and creating the problem. You may need to go into the drain with something to scrape the sides and rinse it with vinegar. I had it come back but finally got rid of it by cleaning it out with a brush dipped in vinegar. It hasn't been back for several years now.

Oops, I hope that statement didn't jinx me.

Bill

The internet has people suggesting pouring hot water down the drain first, then one cup of baking soda, and one cup of vinegar to create a bubbling volcano inside the drainpipe. alternatively, pour one cup of table salt and one cup of vinegar and let sit overnight.

First would bubble up to clean the down pipe.

The second will work if the odor is mostly in the trap. If the down pipe is coated a brushing of that solution would be a good idea.

I think I may have water being sucked out of a trap. Since yesterday I turn on sink and tub for a cup after a flush. Oder is completely gone. I might attempt vent access from the basement but I have a fear of breaking a roof seal.

I am the viper. I will be there in 20 days. I will bring mold.

If the water in your trap is being sucked out, that means a length of the drain pipe has become very narrow. The narrowing of the pipe may be quite far down the line. Water can still pass through, but it will be able to act as a siphon hose, so after you have flushed the toilet, the water in the narrow pipe will siphon the water out of the trap.

The only solution is to clear the debris that's coating the inside of your pipe. If you use a snake, that might be quite a professional length of snake you will need.

I have one idea that might work if it's really the case that your pipe has narrowed due to gunk coating the inside.

First you try the baking soda, vinegar and salt trick at night when nobody uses the shower and toilet. Do it many times so that the baking soda and vinegar can penetrate a long distance down the pipe.

Next you need to plug the drain holes in the shower/bathtub and the sink, because you are going to use a plunger to work on the toilet. You need to plug the other holes so that the water/air pressure won't escape from the other holes while you are plunging the toilet. You can try to push wet cloth down the hole and then put some heavy object, like a bucket of water, to sit on top of it.

This accordion bellow type of plunger can hold a lot of water/air.

Why am I going to plunge the toilet?

I imagine all of drains are connecting to the same pipe down the line. You need to use water/air pressure to push/loosen the debris coating the inside of the pipe. Plugging the other smaller holes and plunge the larger toilet hole is easier work.

Thanks for explaining.

Can also be due to the vent being blocked.

But if the blockage sees gunk backing up all the way to the floor drain, you will never be able to get baking soda and vinegar separate down to the thinning so that it can blast the gunk out.

I hope it works.

If the narrowing of the drain pipe is cleared, you should notice your toilet flushing fasting and stronger. The speed of the water coming out of the tank is affected by how fast the water can pass through the P trap, which is affected by the overall speed water can pass through the drain pipe.

Maybe yes and no. The speed of the water coming out of the tank could not be affected. There is an air gap.

However the speed of water going down the hole could be. That movement is caused by the siphon effect.

Usually vent access is done from the roof, running a water hose or snake down it. They are open and over time leaves, debris, etc could clog it.

Intuition would tell you that the water coming out of the tank is gravity fed, so the speed of the water coming out of the tank would not be affected by the speed of water clearing the P trap, but for a long time my toilet was weak in flushing and finally it was totally clogged up after I poured something down the toilet instead of the garbage can. I had to use snake and plunger to clear the blockage, and then I was surprised the toilet became much more powerful in flushing. The water is coming out of the bottom and the rim of the toilet bowl so fast that it is making a powerful swirl every time I flush. (Amazingly it even affects the jets of water coming out of the rim)

One possible way to explain this phenomenon is called "back pressure". The tank water coming out of the opening at the bottom of the toilet bowl starts a whirlpool action to propel the water into the P trap. The whirlpool action also helps in pulling water out of the hole so you get a more powerful flushing action if the drain can pass water unrestricted.

If the toilet is partially clogged, the water will rise inside the toilet bowl instead of making a strong whirlpool. The water in the tank will still come out but at a lower rate due to "back pressure" at the opening at the bottom, and theoretically the relative height the water in the tank is dropping into the toilet bowl is decreasing due to the rising water level inside the toilet bowl.