I have a weird issue with a Viessman 100-w combi boiler whereby it has recently started to make a loud thud when switching CH to DHW (sounds like water hammer). I'm almost certain it is the diverter valve. and its coming from that region when the cover is off. It does not happen the other way around (DHW => CH). I've noticed its worse when heating is low, < 30c, and doesn't happen as frequently above 35/40c - but I've not confirmed this.
Any thoughts on what it may be ? initially thought it was the EV but topping it up did nothing. Cant see any loose pipes, they are all clipped. It was very quiet when first installed it about 2 months ago so seems like possible wear/tear.
Could it be limescale ? I am in a hard water area, but the incoming water has a mag limescale disrupter. I'm hoping this isn't a design flaw or something.
Any thoughts on what it may be ? initially thought it was the EV but topping it up did nothing. Cant see any loose pipes, they are all clipped. It was very quiet when first installed it about 2 months ago so seems like possible wear/tear.
Could it be limescale ? I am in a hard water area, but the incoming water has a mag limescale disrupter. I'm hoping this isn't a design flaw or something.
