Sulfur smell coming from the shower drain

[HandyGuy]

Here's some quick background information:
The ADU was built on slab foundation some 40 years ago and tenants were living there for a long time. I purchased the house 1.5 years ago.
During Covid, the one bedroom unit was unused for roughly 6 months as the tenant was working from a remote location. A new tenant moved in to the unit in November and a new hot water tank was installed end of January. The unit only has one vent going thru the roof (from the bathroom) and I am certain the ADU sewage line is connected to the main house in the front.

Problem:
By mid February, the tenant told me that he was noticing a sewage smell from the shower stall about 10 minutes after having a shower. He also sometimes smell it when he uses the bathroom sink.

What he did so far:
Pour bleach, baking soda, vinegar, etc. The smell went away for a few a week and came back after that.

Plumber/Rooter opinion/suggestion/recommendation so far
Bunch of plumbers / rooters stopped by and gave me different stories
- I don't know what it is. You need to call a rooter.
- You need a new vent but I don't do this job
- Unfortunately I don't know what is causing the problem
- It is a code violation and the problem could be with the P trap and it is not going low so you need to look at or build a septic tank
- You need to gas the place to see where the problem is
- I think the pipe is broke somewhere bu I can't use my endoscopic camera as it won't show anything

Before going on this goose chase, I would like to get your expert opinion. Appreciate your help.

Thanks in advance.
Best.

 

[Jeff Handy]

What is the zip code?

Are you on well water?

The stink could be from the water heater.

I would have the drain rodded out anyway, at least to where it joins the other dwelling’s line.

Are you on septic or city sewer?

Showers and bathrooms tend to clog, have both the toilet and shower drains rodded now, before you have to do it on a holiday, in an emergency, at higher rates.

 

[arctic bill]

Is the p trap holding water. put some thing down the drain that is staight it should come back wet. if not then something is wrong with the trap. Could be venting or a leak through the trap .

 

[Danny3xd]

Just to add.
How strong is the odor? Bleach and the like kills the bacteria. Can you post pictures? Given the information and if nothing else is backing up. I'd snake it. Can get snakes for that sized line pretty cheap.

Is it the lowest drain on that line? It could be possible the main is restricted, partially blocked.

 

[HandyGuy]

Thanks for your response. Please see answers inline..

What is the zip code? 95130

Are you on well water? No

The stink could be from the water heater. Even though it is a new water heater?

I would have the drain rodded out anyway, at least to where it joins the other dwelling’s line.

Are you on septic or city sewer? City sewer

Showers and bathrooms tend to clog, have both the toilet and shower drains rodded now, before you have to do it on a holiday, in an emergency, at higher rates. - two rooters came by and they did not root it. That's a good idea.

 

[HandyGuy]

Is the p trap holding water. put some thing down the drain that is staight it should come back wet. if not then something is wrong with the trap. Could be venting or a leak through the trap .

Thanks for your response. Yes, P trap is holding water.

 

[HandyGuy]

Just attaching a few photos..
Photo 1 shows one vent pipe and one water heater went pipe.
Photo 2 shows the sewer pipe coming from the house
Appreciate any additional recommendations. Thank you.

 

[arctic bill]

Thanks for your response. Yes, P trap is holding water.

then maybe the water smells

 

[Jeff Handy]

Looks like your zip code uses city well water and surface water, which is treated.

Your new water heater sacrificial anode rod might be causing the smell.

It is probably a magnesium rod.

Your plumber can exchange it for an aluminum/zinc anode rod, which causes less reaction to minerals or bacteria that can create rotten egg smells.

 

[HandyGuy]

Both hot water and cold water are not smelling. Will this eliminate water heater?
The smell is confined to the shower drain and I believe there is a vent for the faucet but I don't think there is a vent going from the shower. They just did the fishing with camera this morning and did not see any blockages. Will be doing the gas test today. Should I watch for anything? Thanks.

 

[Geofd]

I'm with Jeff handy on this one , had the same thing happen at work, we changed the anode rod and it went away,it's possible yup smell it in the shower because the water is running longer try removing an aerator from a faucet, running the hot water for a few minutes,reason for removing the aerator is do you get unrestricted flow,trail and error......

 

[HandyGuy]

The gas test showed gas coming from under the toilet seat. Will be replacing the "O" wax ring. Will keep you posted. Thanks again for all your responses.

 

[HandyGuy]

Back to square one. Changed the O ring but the smell is back after having shower. Back to square one.
- The water is flowing from all drains properly - no blockage
- Camera showed no blockage from the vent and from the ground to the toilet and to the kitchen sink
I am running out of options and would love to get your opinion. Thanks in advance.

 

[HandyGuy]

The water heater is only 3 months old (Bradford White - ultra low Nox Series)

 

[Jeff Handy]

Change the anode rod in the water heater.
Then drain and flush the heater, then sanitize the plumbing system with bleach.
You can find videos on how to do it, on Youtube.
Or someone on here might feel like giving a lesson.

 

[GReynolds929]

The gas test showed gas coming from under the toilet seat. Will be replacing the "O" wax ring. Will keep you posted. Thanks again for all your responses.

By seat are you referring to where you put your butt or the wax ring seal? If smoke was coming out of the bowl the trap is being siphoned somehow and losing its seal allowing sewer gas to enter the room.

 

[HandyGuy]

Thanks. The smoke was coming from where the toilet meets the floor so changed the wax ring.

 

[PerplexedPlumber]

Just out of curiosity, have you checked the vent pipe all the way from the shower and toilet through the roof to make sure there is not an obstruction? Or a bird's nest at the top?

 

[HandyGuy]

Just out of curiosity, have you checked the vent pipe all the way from the shower and toilet through the roof to make sure there is not an obstruction? Or a bird's nest at the top?

Thanks. Yes, they did, with the camera and everything was clear.

 

[HandyGuy]

I am running out of options. The next (last) thing I am trying to check is the type of anode rod used in the water heater. We have two same brand water heaters in the house. One was installed last August and other this Jan. I will be reaching out to the mfr to find out whether there is any difference in the anode rod material. Will keep everyone posted.