I have managed to clean out the copper piping by detatching both ends then connecting the incabin end to the freshwater hot water
tap inside. I cleaned out the piping by squirting some dishwashing liquid into the connecting hose and then turning on the tap. I repeated this several times and then flushed the piping with plain hot water
. Then I connected a scuba
tank to the opening and removed any residual water with high pressure air. There was quite a bit of oily residue that came out of the pipe and it seems to be working quite well but time will tell.