1928 home on city sewer. After showers there is a septic smell coming up from floor dain in basement. I have oured enormous amounts of water down the drain not fixing the problem. I ended up cover the drain with a bucket, this took care of the smell, this was all three months ago. I recently cut my gutter down spouts and added downspout extenders. WHile doing this my wife was taking a shower and that awfull septic smell was coming from one of the downsput drains in the ground. I went inside and rmoved the buckett from the floor drain in basement and the smell was there as well, however by removing the buckett the smell outside coming from the downspout drain ceased. 1) what could be causing this? 2) should I have left the downpouts alone, and let them drain into wherever that drains leads to? 3) I do have one stack vent on roof of house, could this be clogged and causing the problem?
Thanks, any advice is much appreciated.

It sounds like you may have had the downspouts connected to the city sewer and when you removed them, the basement drain was higher and acted like a vent. Are you sure there is a trap in the floor drain? This was built 80+ years ago and who knows what was done. Pour water into the floor drain and see if someone else can hear water running in the downspout drain. That will tell you if they are connected. Not really a good practice since the waste water treatment plant is processing basically clean water and during heavy rains can cause overflows in the plant. Now, pour water down the downspout drain and see if you can hear the water running in the floor drain. If you can, you most likely don't have a trap or it is disconnected or broken and you are direct venting the sewer into the basement. Floor drains in basements are not encouraged because they are the first place to flood during a backup. Do you need this drain? If not, jam a big rag or paper wad in the drain and mix up some quickcrete sand mix and fill the hole.

Well, running water through the gutter drain I did her water under the floor drain in basement. I could not hear any water from the gutter drain when fluching water through the floor drain in basement. However, when running the shower/tub I could hea