A
Hi - I did put in the Ethos 54C and it's totally fine, though I must say I haven't yet ever had two showers running at the same time, so I can't really tell you whether it works. My real problem is the flow rate of the water supply itself, since I had an incompetent plumber scréw up all the pipe-work for me. But the Ethos heats 12l/min of water coming through my shower without any trouble at all, for what that's worth.