A recent batch of grain-brewed ordinary bitter had a pronounced chlorine or TCP flavour. I used the same water treatment that usually works - boil, campden tablets, stand overnight. The recipe was straightforward, pale and crystal malts, columbus, brmling cross and citra hops and wyeast ale yeast. Fermented 8 days then racked into cask. After 2 weeks in the cask it was flat, cloudy and chemical tasting. I don't use chlorine sanitiser. Any thoughts on the problem?
This sounds like it could be chlorophenols (typically perceived as plasticky / band-aids / medicinal / chemical flavors). If you're not using Chlorine-based sanitizers, this may have been caused by a wild yeast or bacterial infection. The fact that you also noted flocculation (cloudy) and carbonation issues is generally in line with the notion of an infection.
You can do some further testing to attempt to narrow down the cause or point at which the infection was introduced:
- Forced wort test: Prepare a small, sanitized sample jar and transfer some of your unfermented wort into it but don't pitch any yeast. If the same off-flavors show up in this sample, it'd indicate that you have something wrong in your mashing / boiling / cooling process.
- Bottle some of the fermented beer at the same point you'd transfer to your cask and compare to the casked beer.
- If your plastic lines used for transferring between vessels / fermentors / casks are old, you may want to simply replace them.
Lastly, what type of cask are you using and how are you sanitizing it? Typically a combination of a caustic or PBW first with a sanitizer second is more effective than a single one-step product. (http://www.fivestarchemicals.com/breweries/homebrewing/products/)
My best guess is that your water, while standing overnight, contracted some sort of wild bacteria or yeast. In the future I'd purchase 5 gallon jugs of water at your local grocery store, and use those to brew. I've never had a problem. When I brewed with tap water (my first 2 batches), I did notice a bit of a chlorinated taste.
Alternatively, your cask may have infected it. How have you cleaned the cask? Acid wash is typically a good choice.