[Tagging] RFD pipeline sub tag substance

[Warin]

Request For Discussion

http://wiki.openstreetmap.org/wiki/Key:substance

Pipe lines currently exist for non drinking water in various part of the 
world. And have done for some time. They are becoming more numerous as 
efforts to save water and reduce environmental impacts increase.

Unfortunately this does not have a tag for non drinking water .. 
possible values could be

non-potable_water

grey_water

Not recycled water as that is too restrictive .. it could be from a 
river/lake that is not suitable for drinking. Or even rain water that 
has not been checked for drinkablity.

I note that"if the medium of a pipeline you are tagging is not listed 
here, please choose a meaningful value at your own discretion."However 
that will lead to multiple values all meaning the same thing or be too 
restrictive.


Should this be a 'RFC' as in a request for comment?

According to taginfo the values in decreasing use are water (30%), gas, 
heat, sewrage, oil, hot water (20%), electricity (should be 'cable' 
according to the wiki), sewage (3%), oxygen, coal, lng, fuel.

I note This tag has a status "unspecified' .. that probaly means it has 
not been voted on here.