I'd say you can, since an enchanted is technically thaumaturgy - the main block on using elements that you're not familiar with in combat is time - Harry's gravitus spell would technically be combat thaumaturgy. Since you don't have to worry about this with an enchanted, as the spell is already keyed up and ready to go, I see no reason why you can't have an enchanted with a Water evocation in it, if you can have an Enchanted that summons a construct (and you can, technically).
EDIT: YS279 says 'Nearly any effect within the realm of Evocation or Thaumaturgy is allowed', which suggests that the normal element restrictions are waived.
Look at it this way: when you're using an enchanted item, you're not actually using Evocation, you're triggering thoumaturgy you did earlier.