Water tanks are heavy when full—hundreds of kilos or more. If they sit directly on the roof slab without proper stands or supports, that weight is concentrated unevenly on a small area. Over time, it can stress the slab, cause cracks, and create seepage issues below.
Tanks placed on proper metal or concrete stands with load spread sensibly show that someone considered structural and waterproofing needs. You might also see better pipe organisation and easier access for cleaning.
Badly placed tanks are like heavy suitcases dumped on a thin shelf. It might hold for a while… until one day it doesn’t.
