The elbow connector on the indirect HW cylinder outlet looks to have gone a bit porous, a build-up of scale on the outside, but no sign of leak from the joint to pipe. Also looks coppery colour in this area. Anyone know what causes this?
It will indeed be a leak at the joint: a very slight one, and the small amount of liquid emerging will be evaporating off (due to the warmth) before it has time to pool, so you never actually see it. When the liquid evaporates, any dissolved materials stay behind and build up, as you are seeing.
Alternatively, there used to be a leak there but for whatever reason, it's cured itself and stopped!
David
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.