You can use copper pipes, but many tradesmen recommend plastic, but with brass retaining nuts and sleeves. Plastic pipe is more pliable and lessens the risk of crimping or leaking, and isn’t prone to corrosion which can lead to problems and costly repairs later. Another option is a stainless steel pipe which is likewise flexible and less prone to corrosion. The only problem with stainless steel piping is that it can cost double the price of copper.