For $30 at Mitre 10 or Bunnings, you can buy a hand-crank auger. Feed it into the pipe until you feel resistance, then crank to grab the hair or sludge. This works wonders for shower drains.
A slow drain is annoying. A fully blocked drain is a health hazard (and it stinks). If you’ve tried the vinegar trick and the plunger and you’re still standing in water up to your ankles, don’t wait until Monday. drain unblocking nz