Viessmann Vitomax LW Operating And Service Instructions page 14

Normal operation
Notes on condensate drainage
During operation, acidic condensate forms in the boiler
and flue pipe. With gas combustion, the pH values are
between 3 and 4. Drain off condensate in accordance
with regulations.
Condensate from systems > 200 kW must be neutral-
ised. Condensate is treated by a neutralising agent in
the neutralising system once it is discharged from the
system.
14
The neutralising agent raises the pH value to between
6.5 and approx. 9.
Code of Practice DWA-A 251 "Condensate from
condensing boilers"