Common causes of toilet tank cracking include blunt force trauma, poor repairs and excessive age. Cracks due to age and botched repairs often develop slowly. According to RedBeacon, any of these cracks are repairable if the crack is discovered while it is still small. Extensive cracks, however, usually render the tank unusable. In these situations, the only option is toilet replacement.
Toilets are susceptible to damage from sharp impacts. Common causes of impact-related toilet tank cracks include falling bathroom cabinets and dropped hair appliances. Single hairline fractures caused by these forces do not always require professional intervention, but the toilet must be replaced, however, if the entire unit is dropped during installation or removal.
Writing for About Plumbing, master plumber Aaron Stickley reveals that poor repairs are another common cause of cracked toilet tanks. For example, excessively tight bolts connecting the tank to the bowl eventually generate cracks, especially if the toilet is old. Repairs may also cause impact injuries if the tools are dropped on the toilet during the work.
The likelihood that a toilet tank will crack increases with age. These cracks often develop near the juncture of the toilet and the floor. Left unrepaired, these cracks eventually turn into leaks with the potential to damage the floor. Water from a cracked, leaky toilet in an upstairs bathroom also has the potential to damage the ceiling of the room below.