How long have you lived in this house? Has the odor always been present and as strong? Have you routinly poured 1 gallon of water in all the drains twice per month? How do you know the smell is from drains instead of elsewhere? How do you know there are no traps?

We have lived in the house about 7 years. We have noticed the smell before but seems lately it has gotten worse. I usually try to dump water down the drain about once every other month. The furnace and AC drain lines run across the floor and into the drain so there is always some water going into the drain. I have looked down the drain with a flash light and it doesn't appear to have a trap. The smell is coming from the drain because i can smell it stronger when I put my head close to the drain.

Ok,it does appear the drain(s) are the problem. The reason it might be intermentint is because there is no condensate from furnace during heating season and very little at low humidity during cooling season. Two reasons come to mind why it might get worse over time. A vent stack may have become obstructed and is why the shower/washer pushes gas out through drain. If you have a clean-out on the main,open it and look/listen while somone use's a garden hose to flush the vent. If you don't soon see/hear water going passed clean-out,have someone going through house looking and listening to make certain water isn't coming into house from broken vent pipe. If vent checks out ok,try flushing floor drains with bleach water. Triple the ratio suggested on container for general cleaning and disinfecting. The water from AC unit will charge the trap but will alow organic growth within the pipe/trap. Bleach kills much of the organic growth on contact. Object(s) that easily float can be used to cover drain and still alow water to enter drain in the event of flood.

This post was edited by klem1 on Mon, Oct 28, 13 at 17:14