I own a 100 year old house with Radiator Heat, I have noticed that every winter I start to smell sewer gases coming from the basement. I pour water/bleach down the drains in the basement, but it never really takes it away. Do I need to worry about replacing the traps? If so, how expensive would that be? Any ideas would be greatly apprecaited.

I would suppect the vents and stacks in the walls before replacing the traps. Odor tends to get more heavy in cold or rainy weather so it could be drifting down from above. Good luck, Tom