A homebrewing friend of mine has been sampling some of my beers and finding that there is a plastic taste in them. I've been looking into it and it seems the 2 most likely explanations are an infection or due to using tap water. I haven't noticed the issue myself, so for some reason it just leads me to think it's more the water issue (if it's the same water I drink on a daily basis, would I notice it?). Another thing my friend noticed is that the more aged beers he's been sampling has the plastic taste even more than the younger ones. Would this fact seem to support the water issue or infection issue? I plan to both do a thorough cleaning of my equipment and use bottled water next time, but I'd still like to know what's causing the issue.