The hot water spout discharges brown water, it can range from light brown to dark brown depending on what I believe is length of time between flushes. This only happens on the hot water, not the grouphead or steam wand on a Heat Exchange unit.

For backstory, I've flushed the system out many times and the water resolves to clear then back to the spectrum of light brown to dark brown within a week or so. I've taken it in to a local service shop and they can't see what is causing this. Additionally both the shop and I have worked through multiple cleaning options but cannot seem to resolve the brown water long term. What you see in the photo is about 1 week post flush and clean.

Does anyone have any ideas/suggestions to resolve?

Thanks,
Andy
(In Chicago if service shops are known)

Wow, that's really coloured! I don't know for sure why, but I have a theory. That machine is one of the few with a nickle plated copper boiler. My best guess is that the nickle plating has become compromised. I'd stop trying to descale it and live with the coloured water. I bet in time it will clear up. Copper is a common, and expensive option for espresso machine boilers. With use, they develop a patina of copper oxide; the copper oxide protects the copper. Since the BZ07 is an HX, there's no danger that the coloured water will get into your coffee, as the brew water passes directly from the reservoir through the HX to the group, without mixing in the boiler. Also, since steam is, well steam, it will be pure too. If you need hot water from your machine, put the water in a foaming jug and steam it to the temperature you need. I'ts a much better option for tea and americanos than using boiler water IMHO.

Thank you for the detailed response. I think you're correct as I noticed the brown water after getting my machine back from an independent shop that had it in to repair some unrelated electrical work. While there, they did a full tune up and descale so I would assume something was done that altered the copper. I think I will periodically flush the HX water through the spout and hope that it eventually clears itself out, I only used the hot water to pre-heat cups anyways. Really appreciate your time and explanation, thanks again.