There are several possible sources of plastic taste and odor issues. One is from plastic pipes used for building plumbing. When water has sat stagnant in the plastic pipes, it may absorb some of the odor from the piping. To help alleviate the problem, flush the pipes before using the water for drinking or cooking.
Another source of plastic taste and odor is from our source water. Occasionally, source water algae blooms occur in our supply reservoirs. When this water is treated with ozone and chlorine at our treatment plants, the resultant taste and odor can seem somewhat plastic or vinyl like. Flushing will not alleviate this problem, but the suggestions listed above for earthy/musty taste and odor may help.