StevieB

I spoke directly with Vaillant tech who informed me that glycol is not needed if you have antifreeze valves - they changed their policy recently. These valves only come into play if you have a very cold day -5C and a power cut for a prolonged period at same time. I have now argued with my installer and won them over to fill system with softened water (only cos I have w/s fitted on cold rising main) and inhibitor only and fit a/f valves. In most installs, unless prolonged power cut in winter is experienced, a/f valves are just insurance. Save on the loss of efficiency caused by glycol and its alternatives AND cost / dangers associated with disposal.