The only reason why building or any society water tank needs waterproofing is water leakage concern. Water tank is a concrete structure constructed above the beam, layered with bricks. This is the joint of water tank to the building where waterproofing generally needs to be done. Cracks in water tank too start developing from this joint.
Usually there crack in water tank are formed internally. External crack formation is very rare. Sometimes it’s very difficult to detect exact location of the crack. For as per water capillary action, the crack could be somewhere else, but water could have traveled and affected other area or wall. The exact location of the crack can be known only on breaking the plaster of the internal wall. You could be startled when I said that plaster needs to be broken, but here the plaster of entire water tank is not broken. Only the affected area plaster if broken to know the exact crack location.
To seal the crack in water storage tank, EPOXY is used. An EPOXY grouting is used to seal the crack followed by covering ti up with a plaster. EPOXY is a premium waterproofing material used to seal cracks and waterproof heavily constructed structures like water storage tanks, Dam walls, bridges, etc.
At times crack development is not the reason for water leakage. In such situations, the water storage tank is treated with a layer of polymer coating followed by polymer cementing. After polymer treatment, plastering is dine to fix the waterproofing treatment.
There are a few contractors how use RCC polymer for waterproofing terrace water storage tanks. But using polymer compound cannot solve water leakage problems for such huge structure. The crack that has developed in water tank will be as deep as 10inches to 1 feet that a RCC polymer cannot resolve the water leakage issue.
Waterproofing the water storage tank roughly takes a 5-6 days. This will include emptying the water storage tank, drying it, waterproofing the affected area and final drying of chemicals and plaster.