Is there a tileID for water? And/or is there a way to place water with the use of an item?

[NinjaKitty]

I'm trying to create a clentaminator fluid that converts air into water, but I'm clearly having difficulties. I'm fairly certain I can use voodoo magic to detect air as a tile, but I dont know how i would convert that air into the water tile. Any help would be appreciated, if it's not possible then let me know.
Also, if you need me to post the code for the fluid/spray then let me know.
thanks.