We have 4 private showers at our building Two for each bathroom with the drains side by side for each bathroom. There is a public accessible restroom on the back of the building. No showers there, just toilets.

The flow of the line goes: Public bathrooms>Our showers (shower 1>shower2)>our toilets>out to street sewer.

Shower 1 in the men's restroom is emitting a sewer smell. There is no crawl space or anyway to visibly examine the line. There is water visible in the drain and it seems to be slightly moving - no water draining from the shower - which is making me wonder if that is a visible indication of gas coming up?

The other drains done exhibit that, despite water also being present in the drain.

That there is water present in the drain is smelling, isn't that indicative the trap is good/not broken?

Any tips on how I can possibly diagnose what the issue is?

 

If the showers aren't used routinely..... the water in the trap evaporates.
You can add water to the trap to stop that.

 

Remove the grate and shine a flashlight down into the shower's drain so you can clearly see the water in the trap. It should be still. If you see bubbles it can mean you have a clogged vent line or possibly a partial clog in the drain line.

 

The showers are used daily.

I did lift the grate and saw the water. I didn't see bubbles but there was some movement to it.

I do routine snaking of the drains to remove hair and didn't find anything in that drain last time I did it which was a week or so ago.

If it is a clogged vent, would only that one drain be experiencing the issue?

 

If it is a clogged vent, would only that one drain be experiencing the issue?

It depends on how the plumbing is run. Or it could be that that trap offers the point of least resistance. If you used a plug and capped off that shower's drain you might see the problem move somewhere else.