Hello,
Ive seen this before when the drain has a proper p-trap seal but there's a bacteria or something that keeps feeding a smell at a p-trap... Many years ago had the perfect solution or drain smell product but cant remember what it was... Anyone have a good solution they use?

Thanks

Those are probably drain flies. Does the tub go unused for days? Drain flies are harmless. Making sure the trap has water in it should keep them from getting out. Almost anything that cleans will kill them. I used borax - it's cheap and I have it on hand. Making sure the trap doesn't run dry should keep them out. When I kept my shower water in the tub and bailed it out to flush the toilet I got them.

Hi,
Thanks. I have not used borax.. I'll give it a try tomorrow. Years ago I've come across what seems like a bacteria that smells and is really hard to kill with just the standard liquid solutions, bleach ect.. This tenant says it smells really bad. Long ago I had found a product that would kill the smell when all other products fail... lol, cant remember what it was.

If the trap frequently runs dry, an S-trap is often the culprit. They are no longer allowed for this reason.

The symptoms you describe are of an empty trap. When you solve that you solve both symptoms. The trap is dry for one of 3 reasons: 1 - the drain is rarely used so dries out (happened to me when I used my tub water to flush the toilet); 2 - it is an s-trap, as DaveMills mentions; 3 - there's a leak. If all you do is pour some stuff down the drain that will work only temporarily. Maybe the tenant rarely bathes? Pour a cup of soapy (or boraxy) water in the drain, put the plug in to slow evaporation.
Attach a piece of cloth on a straightened coat hanger (or something both rigid and flexible). Stick it down the drain - does it get soaked?

Hi, Thx.. this is a standard 2" abs trap ... Holding water properly.. .I can see in the riser with a flashlight.. its totally sealed no water level bouncing when sinks or toilet is flushed.. . i scrubbed out the riser with a brush and treated it. I was really just curious if Plumbers are coming across bacteria on the slim occasion and what products they use.

The water in the trap is the only thing that keeps sewer gas from coming up your drain. Drains are ideal conditions for drain flies to live in; you can clean them out once, perhaps, but they'll come back. Water in the trap also blocks them. If your vent is blocked sewer gas can build up enough pressure to push through the trap's water; perhaps drain flies can hitch a ride on the bubbles.

Hey, Thank you.. Good thinking!