It sounds like you have a condensing furnace. These type of furnaces have an operating efficiency of more than 90% and produce condensate water as a waste product.

If the drain is gurgling it may have a blockage. The condensate may be tripping a condensate safety switch. This prevents a flooding condition by shutting down the furnace.

Does the condensate line have a trap and a clean out plug? If not you may need to take apart the drain in order to clean it.

mike - thank you! could you look at this pic and tell me perhaps where i should be looking and what i might need to do?

i guess what i'm trying to figure out is whether i can do this myself before i call in the special forces! lol just need to know where to look and what to do!

The bottom black pipe is the drain the furnace. The drain above is for the AC coil.

Can you pull out the black hose going into the PVC pipe? Check the black hose and PVC elbow for clogs. There are flexible wire brushes made for cleaning PVC drains.

Also check the PVC line is properly pitched all the way to the drain. Pour some water in the open PVC pipe and see if it is draining properly.

hi mike - yes i believe i can pull that hose out. and i assume you mean pour some water into the pipe i removed the black hose from and see if it drains quickly.
but would i be correct in assuming that that loNG pvc pipe from the condenser at the top is OK? the issue is with what happens closer to the drain? thanks so much!

mike - i pulled that black hose out and took at small plastic indoor plant watering can and poured quite a bit of water down that pvc pipe and it didn't back up! i fired up the heater and the glow plugs ticked on and started to glow but then the glow plugs stopped glowing but after another 30 seconds of so, everything ignited fine (BTW replaced glow plug a few weeks ago. now, i didn't hear the sloshing water sounds, but sometimes it won't be so loud or distinct. if it's not the drain, maybe a bad switch or could that switch be tripped by something at another location in the system? thanks again!

The upper line appears to be an AC condensate line.

I doubt you are running the AC now.

Check that black hose carefully. If you can disconnect from the furnace give it a good flushing. The bend of the hose seems tight. I imagine it could get clogged over a period of time. From the picture it looks like it is not pitched downward from the furnace to the PVC pipe. The water will not drain properly without a downward pitch.

hi mike - i removed that smaller black hose and it's clear. here's was just happened, though: started the heater and i immediately heard gurgling noises from the drain area - pulled that hose off and a small amount of water got pumped out but then quickly stopped - HOWEVER - even with that hose off, i STILL heard gurgling noises from the drain - could it have anything to do with that long pvc pipe from the condenser which as you can see is connected almost directly (in the back) to that drainpipe which disappears into the wood base? as i said with that smaller black hose disconnected, still hearing a gurgling noise and the heater won't fire the glow plug. thanks so much!

If you remove the black hose from the PVC pipe you should see water flowing from the furnace when it is running. If the furnace does not fire, then you probably have some other problem. You will need to call in a tech for a diagnosis.

The gurgling sound in the PVC pipe may mean you have a blockage further down the line. It could also mean the drain pipe does not have enough air ventilation.

You might also look at the trap above located beside the AC unit, that section of elbows and straight pipe. When mine starts making gurgling sounds when heating, it is this trap getting low on water. I just pour a little more in and that takes care of it.

hi - how do you pour more water into it? you mean those pipes that come down from the condenser unit above?

The cap on the vertical should not be glued, just pushed on.

It is a taper though.

If a gorilla pushes it on you may need pump pliers to rotate it back and forth while you also pull up to get it off.

This post was edited by brickeyee on Fri, Feb 15, 13 at 13:39