no room in a modern vehicle... Should've added.

if you get one of the dessicant filter heads that have a dedicated purge back line they also have an open to atmosphere port on them, when the pressure is not coming from the pump the cartridge is open to atmosphere, if you were to put it near an exhaust manifold/turbo that would nicely dehydrate the dessicant for you extending the life of the cartridge, HOWEVER, those type of filter head come somewhere north of "thats a bit bloody pricey" cost wise.