QUOTE=redgoat67]Hello,
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

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Originally Posted by redgoat67

QUOTE=redgoat67]Hello,
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

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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[/QUOTE]
Both pipes should be pitched (angled) over their total length so that any water that accumulates within them from condensation of flue gas or intrusion from the exterior flows back into the furnace. There it is routed to the condensate drain line along with condensate from the heat exchanger and sent to drain (I'm not familiar with your model number, but since you have a PVC flue pipe, it must be >90% and condensing). Is there a low spot in that run of pipes where water could accumulate? Although I can't envision it being deep enough to slosh like waves. Maybe there's another issue other than a low spot in the flue line. When the furnace is running do you see water draining in some manner. Either a drain line directly from the furnace into a sump or out the side of the house? Or maybe into a small (ca. 1/2-1 gallon) box (sump) at the base of the furnace with a pump on it. The pump would run periodically to send water in the box to a drain whenever the box becomes filled with water. If you are not seeing water draining from the furnace when it is running, then it may be that the drain line is substantially clogged and the sound you are hearing is flue gas passing thru/over the accumulated water. In fact, even if it is only partially clogged you may be seeing some water drain, but too slowly to keep up with condensation during heating. So water accumulates and makes noise while the furnace runs (some of the water drains during that time). I would look into cleaning out the condensate drain line first. There should be a press-fit PVC cap somewhere near a trap in that line. Remove the cap and try cleaning out the line with a heavy wire.

A 90% furnace will have water in the vent pipe,condensation drain and inducer housing while running. If the heat is working why worry. If I had a condensing furnace I would worry if the sound of water was not their that means no heat.