I've been experiencing a ongoing problem. A strong plastic off taste when beer sits in my line for more than about 2-3 minutes. I know the beer coming out of the keg is ok, and I can drink it as long as I avoid leaving any in the line. The small amount of beer in the line also foams up violently when released into the glass. But I've changed my lines about 4-5 times, used different taps, guns, stripped discos, taps etc. PBW soak, etc, etc. Other people do not have these problems with the same line types (poly, vinyl etc), as I have witnessed it myself drinking their beer. I can understand a small taint, but mine is extreme.
My question is: can something in my beer (PH, high sodium brewing water, etc) react with the typical beerline materials to cause plasticty taste problems?
Any ideas?