Hi I'm new to the forums here and to home improvement. My husband and I just bought our first "fixer upper". So far it's been a learn as you go process. Anyway we have a ranch with a downstairs half bath that has a horrible smell coming from it but only some of the time. I got some advice and have read the posts to this forum. First we replaced the wax seal but that did no help. So is my next step to check the vent on the roof for blockage there is a bad smell coming out of that also. If there is a block would I even be able to see it? My upstairs kitchen sink is a double sink and one side has a garbage disposal that has not been working lately and that side of the sink drains very slowly. Could that be part of the problem? Any help or suggestions are greatly appreciated. Michelle

Can you localize the smell to the toilet? Is there a floor drain in the bathroom?

Are you on city sewer or a septic tank? Do any of your bathroom fixtures "gurgle" or "burp" when you drain water? If you have a blockage in your vent it may be where you can't see it from the roof. While floor drains are required in public bath rooms I've never seen one in a home so we can discount that. What fixture smells the worst? Where's the smell coming from? Do you live on the side of a hill where you might experience downdrafts?
Let me move on to the kitchen.
Have you tried the red reset button on the bottom of your disposal or is it stuck so that it just hums when you turn it on?
The food that's lodged in the disposal's rotting and that's a major source of a bad smell. If you can't get the disposal to work then clean out as much crud as you can and pour 1/4 gallon of bleach down the drain. I'll wait on your answers. Regards, Tom

If the disposal hums take the hex tool that should have come with the disposal and manually turn the disposal to dislodge any crud. Of course do this while the disposal is off! Never seen the tool? You can buy a new one (or borrow a neighbors) and insert it into the bottom of the disposal. Will clear a disposal if stuck about 90% of the time.

If the motor went out that another story...

Sorry can't help much on the smell from the drains.

I have a septic tank. I unclogged the disposal yesterday yet the smell remains downstairs in the half bath. At this point we have removed the sink and the toilet and plugged the flange . We don't have a floor drain and nothing else in the house is gurgling or burping (besides my 1 year old). Even before we took the sink and toilet out they were draining fine no problems just a smell. We can tell the smell is coming from that room somewhere, although it will waft around . We were remodeling the bathroom anyway so it's down to studs and floor. Do you think it could be a crack in the vent somewhere? I know there is a smoke test you can do and the peppermint oil thing to check for a crack but is there anything easier? Anyway I really appreciate everyone's time. I am thankful for any and all help. Michelle

When you plugged the toilet did you also plug the lavatory trap? That's connected to the sewer too.

No I didn't know there was a lavatory trap. Where would that be. I don't think that has anything to do with the smell because the room smelled before we took the toilet out. Thanks michelle

The "sink" you took out has a pipe coming out of the wall that connects directly with the sewer. Could your smell possibly be mold or fungus in the walls? Tom