I had a phenolic problem for about 18 months, that nearly drove me up the wall. In the end, after many spoiled batches, I traced it to my fermenter. This was the last place that I looked because my cleaning process had been to fill the fermenter with a caustic solution for a week. However, I discovered that you need a spray effect. Moritz had this sprayball made for me. I pump hot caustic through the sprayball for about half an hour - and I have not had a phenol since. It also makes cleaning a hell of a lot easier.