What kind of pipe should I use?

For the hot side (collector to heat exchanger) we recommend the stainless steel corrugated pipe (1/2” or 3/4”). The copper pipe as it can withstand the high temperatures. 3/4″ copper flex pipe is optimal and comes in rolls and is very easy to use. No experience in soldering is needed if you use compression fittings and the flexible tubing can be bent and molded without requiring specials 90 degree and 45 degree fittings. The ends are connected using pressure fittings which are very easy to fasten. For the pipe insulation we recommend only the mineral isolation or EPDM.
We don’t recommend regular plastic PEX piping as the temperatures can get very hot at the collector.