I am on a Septic Tank System, and i just replaced my tolet sink and plug and shower system for the tub. I have this terrible odor, which I think in comeing from the drain in the tub. I even took up the stool, making sure the new ring which I replaced was indeed to be over the drain hole. However, I belive it is comeing from the tub. I even took the drain out and crawed under the house, I saw nothing that I was doing wrong. How do I resolved this problem. Do I have the Hardware installed incorrectley?