This is the external unit of an evaporative cooling unit in an apartment block.
Wondering if it is the calcium in the water that has caused the damage and if…

That's really interesting! Thanks

Yes, good question, the other sides don't have the line like this

Good to know, thanks 👍

Thanks for that, it makes sense

Thanks very much everyone for your helpful responses
I am looking at buying this place in the NT.
Will be going to view it in about a week's time. Thinking I will…

Does
the dark line along the bottom of the brick wall indicate pipe leak in attached photo?