Dear Wiessmann team, sorry that I am writing on English, but unfortunately I don't speak German language. I have a this kind of problem. I belong Vitocal 222G with Vitocell 100 E and use them already 4 years. It is perfect equipment, but twice my cellar flooded because the filter sump (FHPR34-B-AQ) on cold water line bursted. I though that reason is bad quality of filter sump ( 6bars WP), but later I found that pressure it this line increased to 8 bars when Vitocall 222G is working only for hot water. Hot water not for heating floor system, hot water for home needs ( shower, kitchen....). This high pressure (8 bars) damaged my filter's sump, UV water disinfection system-VIQUA and Aquahome 20N. Please for your assistance. Best regards. Nedelcho. Bulgaria.
 
				 
				 
				 
				 Flo_Schneider
		
			Flo_Schneider
		
		
		
		
		
		
		
		
	
			
		
		
			
					
		 Flo_Schneider
		
			Flo_Schneider
		
		
		
		
		
		
		
		
	
			
		
		
			
					
		No, it's between Cold water entrance in the house an the vitcocell 100 normally before safety Valve. It's an standard part, not special Viessmann. I think there's probably no Rückflussverhinderer in your installation. I think you should call an plumber.
@Flo_Schneider
kannst du mal die Bilder online stellen? Danke.
