Leave traps to the pros!
Plumbing fixtures throughout your house have a curved section of pipe which is called the trap. The water that is collected the trap creates a seal that prevents the harmful sewer gas from entering your home.
If you ever suspect that you have a sewer gas leak in your house try to isolate which fixture the odor is coming from. Each time water runs down the pipe it causes suction to keep the sewer gas out, but if it cannot get air from a vent it may suck water out of the trap.
You can try and fix this issue by pouring some water down the drain to try and replace the water and reseal the trap. If this does not fix the problem you may have to replace the plumbing. It is a good idea to leave replacing the pipes to a professional.