To understand where the leak comes from, it is first important to understand how your refrigerator works. The evaporator coils are located in the freezer unit, behind the back panel. Coolant is pumped into these coils by the compressor unit, which is located at the rear of the fridge in most models. As the coolant reaches the evaporator coils, it is transformed into gas -- a process the creates cold temperatures. The surface of the coils becomes very cold. A nearby fan blows air over the coils. The air becomes cool and circulates through the freezer and refrigerator, keeping the food cold.
Frost and Ice
Over time, frost and ice build up on the surface of the evaporator coils. For this reason, refrigerators today have a self-defrosting system that kicks in about every 8 hours. A timer triggers a heater located beneath the evaporator coils to turn on. The compressor turns off, and the heater slowly warms up the coils, melting the ice and frost. The resulting water drips into a pan located underneath the coils.
Ideally, the water dripping from the evaporator coils drains from the pan down a hose to the bottom of the fridge, where it collects in another pan and evaporates with a little help from some warm air produced by the compressor. Sometimes, however, the drain hose or even the pan becomes blocked -- usually with ice. In that case, the water cannot drain and backs up into the freezer or refrigerator, causing the water leak. Where the leak occurs depends on where the block in the drain is located.
Fixing the Leak
Because the location of the clog can vary -- some locations are easier to access than others -- it is best to have the issue diagnosed and repaired by a professional. Still, you can at least check and see if the clog is in an easily accessible area. If it is, you might be able to repair it yourself. If you are comfortable doing so, remove the back panel of your freezer and check the water catch-tray located underneath the evaporator coils. If the tray is full of frozen water, simply remove it and thaw it out. Once you remove it, you can also check the drain hole to see if ice is blocking it. A turkey baster filled with hot water can thaw the ice block. If you can't immediately see the blockage, call a professional.