After showering, the drain in our shower reeks of ammonia. It is not a sulphur smell or sewage smell - definitely ammonia. It drains fine so there's no clog and none of our other drains have this issue nor do we have draining issues elsewhere. We checked the crawlspace for any sign of leakage - nada. Regardless of the non-issue (draining), we have poured chemicals (approved for shower drains) into the offending drain but that didn't fix the problem. We poured a bunch of baking soda followed by vinegar into the drain - again, didn't solve the problem. We haven't yet removed the drain cover and scrubbed the drain's walls - that will be our next move. So, am wondering if there's anything else we should look into that may be causing the problem.