The last two brews I've done on my Grainfather have an off flavour, and I don't know why. The first was Brew UK's Hopback Summer Lightning clone. It had none of the fruity hop flavour that I like, just an odd aftertaste. The second brew, which has just finished conditioning, is similar. It's a Proper Job clone, and it smell fine, but again it has the odd aftertaste. Last time I had a problem, it turned out to be a lump of mouldy grain stuck in the spring in the pump valve. I now make sure I take it apart and clean it after every brew. That caused a TCP flavour, which made the beer undrinkable. This time, it's not undrinkable, but it's not very pleasant. I'm pretty sure it's not happening after fermentation, as I keg half of the brew, and bottle the rest, and it all tastes the same. So it must be in the Grainfather, or in fermentation. I put the Summer Lightning failure down to too high a fermentation temperature, as we had hot weather at the time, but the Proper Job went into my beer fridge at 19degrees C. Any idea what could be going wrong folks? I would be very grateful if anyone can solve this for me.