Plumbing in plastic or copper, which one is best? Plumbing plastic or copper which one is best for use when installing new pipework. Plumbing plastic or copper both have their advantages and disadvantages depending on where there’ being used. Plastic pipes and fittings are most likely found in modern buildings. However, plastic pipes and fittings are commonly used on repairs and upgrades to pipework that has been in place for many years. Plastic is often criticized for being harmful to the e...