Originally Posted by Pete7
Has it got an external filter on it? if so its likely the brass ferrules will be about 5/16ths inside dia. Now thats got you worried, relax. The Opti will be burning about 7.5 gals per hour, so reasonably frugal.
It has - but the connectors are all rusted to hell, so that's being replaced too, and I'm ordering new brass ferrules also. They'll be for 10mm hose as well, 18mm outside dia.
Everything must be replaced