We have a septic system & both well & city water. When it rains we get a bad sulfur smell in the house. Recently I discovered that it was coming from the sump pit. Today we have had quite a bit of rain & the 1st flr bathroom toilet started to bubble. Please help!

Is this a sump pit for basement drainage or an ejector pump pit for house waste water removal? Normally the 2 are not connected. If this is an ejector pump, you may have a blocked vent and the toilet is acting as the vent. Must be a dedicated vent on ejector pumps.