On Wed, 01 Aug 2018 17:27:40 +0100, wrote:

Thanks, to clarify I intend to first empty the galvanised steel cold
water tank and wet vacuum any scale in the bottom. I was only going
to part fill it and would add the fernox DS3 as you advise.

Fernox DS3 is OK on glavanised, I take it?


Thomas Prufer