Actually the cold water extraction does work, since the codeine is water soluble, and acetominophen is not. The acetominophen would rise to the top, while the codeine is left in the water. Just scrape off the crap and drink the water.

There always is a bit of chemical loss with the cold water extraction, unless you are a veteran at it, so you might want to add a little more in when you attempt to extract it via cold water extraction.