From what I have gathered from other answers, the fact that my tub gurgles when I flush the toilet suggests a venting issue. Can this same issue also cause it to drain very slowly? It can handle a five minute shower but after that the water has filled whatever pipe space is available and starts backing up into the tub (which then takes several hours to drain). If I flush a toilet the water seems to drain slightly faster, though that may be an illusion. All that to say, are the gurgling and slow draining possibly one issue, or is it more likely that I have both a drain and a vent problem?