Originally Posted by
hkstroud
I agree with Smoothy about what you have read on the internet
If someone really said that, they should not be allowed to discuss plumbing in any way. Your "common sense" should tell you that couldn't possibly be correct.
There are a number of tub stopper mechanisms, two of which Smoothy has shown. If you have remove the stopper and cleared any decaying hair that might have been trapped in the drain as you have indicated, it is possible that the trap is dry.
There is a thing called a trap, which is basically a low place in the drain. Water collects in the trap and prevents sewer gasses from coming back. Look under the lavatory sink or kitchen sink to see what a trap looks.
First, slowly pour about a quart of water down the tub drain. Then check to see if you smell any odor out of the overflow. If you smell an odor, try cleaning the drain again with the plastic snake. You must not have remove all the decaying hair.
If you smell no odor, flush the toilet and run water down the lavatory sink. Again check for odor. If you smell an odor, you have a blocked vent pipe. As water flows down the drain pipe it must be able to pull air in behind it. If it can't get any air in, the water going down the drain will suck the water out of the trap. The water in the trap is your seal that prevents sewer gasses from entering your home. The vent pipe, which goes up through the roof, is there to let air into the drain pipe.
Do these things and post back what you find.