HELP, My house has two kitchens. One up stairs and one down stairs. My kitchen sink down stairs backed up last night when absolutely no water was being run (2 am)heard some kind of loud rumbles and up it came. Has happened before but always cleared it self I guess. If I run up stairs kitchen sink water will come up in down stairs. Plunged the heck out of but it just gurgles and water comes back up.

Is this a single family home?
It sounds like you have a blockage downstream from the basement sink. Try this, Remove the trap and send s snake up in the wall. You will run into a 90 about 8 inches in but once past that you only have to put out 6 feet more of snake.
If that don't get it then the blockage's farther down the line, This can be reached from the roof vent. Put out enough snake to reach the base and 15 feet more. Good luck, Tom

Do you have a shower or tub on this lower level? I am with Tom so far but try to answer our questions.