When resetting a septic tank alarm, it typically takes around 12-24 hours for the alarm to fully reset. During this period, it is important to reduce household water usage to aid in lowering the wastewater level in the septic tank. If the septic alarm light remains on after the designated time frame, it indicates the presence of another issue with the system that requires attention. Prompt action should be taken to diagnose and address the underlying problem, such as high sludge levels, a malfunctioning pump, a clogged effluent filter, a clogged drain field, or malfunctioning septic system components.