They do have the other material for hot water pipes here now, imported from germany I believe. I have a sample on my desk.
A company called SiamConsulting has it, not sure on prices though. No need for copper pipes anymore and the expense.
However the pool heater I have designed for Khao Yai will need copper pipe as it runs through 2 external heating sources.....fireplace and wood fired oven.
The black pipe coiled up on the roof works a treat....just looks ugly if you can see the roof, if not then go for it.
I like poisoning my neighbours dogs till they die cos I'm a cnut