Asarkar_kolkata Thank you for your interest in our technical discussion forum. Literature sources suggest that the copper alloys in general show good resistance to alcohols. As long as the water portion doesn't contain any contaminents detrimental to copper, 70-30 copper alloy should be ok in your stated service. Copper is not subject to low toughness at cryogenic temperatures, so the -20C service shouldn't be a problem either. Hope this helps! David Hendrix The Hendrix Group Inc.