title_body: How to avoid channels when pouring espresso
upvoted_answer: If the espresso is pouring too fast it most likely means you need to grind finer, not tamp harder.
  
  To avoid channels you first need to make sure your machine's pressure is not too high. 9 bars is the usual pressure, but there is evidence that 7 bars will reduce channeling. Many consumer machines come with 12-15 bars of pressure which is simply too high.
  
  Then you need a proper grinder that will have a consistent grind and not produce clumps, otherwise your cake density will not be even.
  
  Your distribution and tamping must be even. Tamping too hard is not necessary. Some people have good results only using a distributor/leveler and not tamping. Make sure your tamper/leveler matches your basket size exactly. Sometimes you need a +0.5mm or +0.3mm over the written size to actually match your basket.
  
  Finally, make sure your shower and basket do not have obstructed holes. You should use Cafiza regularly to clean your group head, portafilter, etc.