If your air-conditioning system is leaking water, it could be cause by a few scenario,

Your aircon system has been in use for a few years,

1. Drain pipe is choke with jelly and dirt thus causing back flow of condensate and dripping out of your aircon unit
2. The indoor unit is so dirty that it chokes up the internal drain line and cause the blower to spit water out of your aircon unit
3. There is icing forming on your indoor unit, causing water to drip. This is cause by low pressure of the system which has a possibility of gas leaking

Your aircon system is new and only has been in operation for a few months,

1. There is insufficient gradient on your drain pipe, your installer might have install it wrongly.
2. Your drain pipe is connected wrongly
3. Your drain pipe has crack and causes a leak
4. The drain pipe is not insulated and causes condensation at the bottom of your Indoor Unit