I have used this chiller three times now. The first time it worked great with my Blichmann Boilermaker and HopBlocker and chilled the wort as fast as it would drain to 65 degrees. The second time I used it, there was a total failure as the chiller got clogged. If I had been using a pump, I am guessing this would not have been a big issue. However, since I was using gravity, I was out-of-luck. Had to buy a bag of ice to save the batch. On the third try, I drained about a quart of wort from the kettle before attaching the hose to the chiller. A rather large amount of trub came out of the hose before running clear. After attaching the hose, the chiller worked great. I am guessing that a certain amount of hops/trub entered the HopBlocker before I whirlpooled. Once that was cleared, everything worked as advertised.