Oic. But for no reason one will not take a ladder up to see. Any sign that the tank is leaking?
Depending on how serious the leak is, the false ceiling below (or surrounding area), will usually have :
1) a discoloured surface paint colour, compared to unaffected areas
2) rippled/bulging/sagging surface
3) soft/disintergrating/squishy feeling when pressed
You may get all of the above or none - it depends on how serious the leak is.
A small leak may take weeks or months to show any visible signs.
There usually could be a musty smell as well, but you may not notice it if the area is well ventilated.