Question: Why does my shower drain smell like sewage?
Answer: Your drains have vents and traps built into them, and that system is designed to push gases outside of the house. Whenever the ventilation system is clogged or compromised, it stops the gases from escaping.
In most cases, a sewer smell coming from the shower drain is because the vents or drain traps are broken or compromised, or because smelly gunk has built up in your shower drain.
In some cases, like in a shower that is not used much, the shower drainage system may have stayed dry for too long and the vents are not opening and closing like they should. Run that shower at least once a week to keep the vents and traps working properly and the smell should go away.
The other problem can be a build up of bacteria. Use a plastic zip it to remove any hair and build up that has collected inside your shower drain, and then use an enzyme based drain cleaner like BioClean to eat away that smelly bacteria with good bacteria that will keep your drains clean.
What You Can Do
If the smell is coming from a shower drain in a bathroom that is not used often, try running the shower twice a week and see if the smell goes away.
If the smell is happening in a shower that you use often, first check the drain for build up and remove anything you can reach.
Then use an enzyme-based cleaner.
If the smell remains, hire a plumber to examine the vents and drain traps.
Learn about enzyme based drain cleaners.
Learn about drain traps.