I have a Carrier 58SXB100 Deluxe gas fired electronic condensing furnace purchased 16 years ago. The furnace seems to work OK as far as heat output. However, with a recent cold snap of week-long temperatures of near zero, I can hear a gurgling sound from inside one of the large pvc pipes that runs from the outside to the furnace. Clearly, water is in the pipe and maybe some ice as well. One pipe is for intake of outside air. The other pipe is for furnace exhaust of burned fuel (hot air). Why is there water inside one of these PVC pipes? What can I do as a handy homeowner without deep pockets to correct this problem? Paul[/QUOTE]

So how do I check my PVC drain line to see if it is clogged or restricted? Water is sloshing in one of these pipes and sounds like an ocean wave. I've almost considered drilling a small hole in the lateral PVC pipes to 1. determine which pipe has water and 2. drain this pipe of excess water. I hate to pay a technician for something that is probably very simple to correct. Any suggestions on the recommended way to fix this problem? This is not just simple moisture in these pipes. Paul