Hi
I am leaving in chicago I have question problem in my bathtub in my down stairs bathroom bad smell coming from bathtub drain very often .I am not using that bathroom often .even those I regular clean and when smell came I put some time bleach(clorox) running hot water almost 5min. But still same time very strong smell .

I am living in this house from 18yrs.
One full bathroom and other half bathroom.
-5yrs ago in half bathroom we add standing shower.
-since last yrs this smell starts suddenly.
So how I rid out this smell or can help me to find out my problem

Thanks