Yes,but not good choice and no necessary,and so ,we don`t receommend.At the begin minutes,copper is fast to heat up, but after 5 minuts,stainless steel can reach the same heating performance and speed as copper pipe does.After our test on copper coil heater,we don`t suggest to use copper because : 1), Copper tube is easy to corrosion after long time, especially after exposed to high temperatures in long-time burning fire. 2), Copper has a lower melting point than stainless steel, which could be an issue when the wood-fired hot tub coil gets too hot after long-time firing. Also,the angle between two pipe will become very big when heating. 3), Cost: If you still insist on make coil heater by copper pipe,we strongly suggest the copper pipe`s OD should be equal to or more than 25mm,and its wall thickness should be more than 1.5mm in order to avoid deform when long-time firing.Obviously,that cost is a big problem.