Water Leak rear floor area

[lighthouserm]

I have a 1998 V70 that after running the air conditioner, the rear carpet on both sides are soaked. This only start after have the air conditioner repair(heat exchanger). How can this happen without the front carpet being wet. Where is the drian line from the air conditioner located and could the heat exchange be installed wrong. There is no water noted after a rain or after washing the car!