There are plastics that don't add a taste to the water, but they are pretty pricey. Take a look at usplastic.com under the tubing heading; there are things like chemfluor and some others that are specifically designed not to impart taste or contaminants into the flowing fluid.
I had to do a bunch of research into plastics for a chemical pump I was working with and this company gave me a crash course in plastic tubing over the phone. Basically, any tubing you get at one of the local high-volume retailers will make hot water taste like plastic. You have to get more sophisticated. For example, you can go with PTFE (teflon) tubing, and not only will it not add taste, it will be really easy to clean out when something gets stuck in there.
Good luck.