There's also https://wiki.openstreetmap.org/wiki/Tag:waterway%3Dwater_point which might be more appropriate and would imply that.

Or also https://wiki.openstreetmap.org/wiki/Tag:amenity%3Dwater_point

The keys are pretty easy to get hold of (e.g. https://specialkeys.co.uk/lowe-and-fletcher-master-keys-as-well-as-others/114-british-waterways-padlock-master-key.html so I'm not really sure if customers is right).