If you never wipe the drain line for your air conditioning system, then you are really going to come to a time when your air conditioning system will freeze up, however a backed up drain line can cause a lot of problems, however green algae can begin to form inside the drain line if the line is never cleaned, when I was residing in my first apartment, I had a crucial leak, however i came beach home from work and took off my shoes by the front door. I started walking over to the living room and I felt my foot get wet in the hall. All of the carpet in the hallway was completely soaked with water. I called the apartment maintenance staff and told them about the wet carpet. They told myself and others that the AC was really leaking and they would call the repair supplier. The AC repair supplier was there in less than an hour and they chop away the carpet and the padding so they could dry the area. They also used a machine to suck out all of the dirt, debris, and algae from the drain line. They told myself and others to wait an hour before I turn the AC component back to cooling. The sound of the blower that dried the carpet was horrendous and I was awake all night long. Thankfully, the carpet and carpet padding was dry in a few afternoons. After that problem, I tried to find apartments that did not have any carpeted areas; Even though the section dried abruptly, the smell of old, musty water never left the apartment.