My house is 15 years old. It has a high efficiency gas furnace and a Honeywell humidifier. They drain to a hole in the floor. The floor (according to the plans) is 4" of concrete and 6" of compacted ROB gravel. Up until this year I have had no problems with the drain. If my yard is similar to my neighbor's (he put up a new house 3 years ago and dug a basement) there is bedrock shale very close to the bottom of the basement;
This summer I replaced the humidistat and the humidifier solenoid.
This November the drain overflowed. Not knowing what else to do, I put drain cleaner in. It didn't help. I pumped it out and flushed it repeatedly. I came up with a lot of organic looking scum and a good amount of silt. I turned the valve from the hot water line to the minimum that would get some water flowing off the humidifier.
After that, it drained rather better.
The next week a furnace guy came out for my annual cleaning. He said cleaning the drain out was about all that could be done. He attributed the overflow to the ground being completely saturated from heavy rain. (many fields in the area had standing water).
However it still drained very slowly. I tried flushing but there wasn't much else to bring up.

Looking at the hole, it looks like 4" of concrete and then something that was a bit darker than the concrete, but just as hard. I drilled a 1" hole 2" down in the bottom of the drain hole. i don't know what the material is, but it is very resistant to drilling. I flushed all the debris out.

I have been okay for a month, but today it overflowed again. I pumped it out and it quickly overflowed again. The weather isn't much different than any other January.

So... how do I get it to drain better? Yeah, I know, condensate pump. I really don't want to for obvious reasons, and it it hasn't been necessary for 15 years it shouldn't be necessary now. I thought about putting a condensate pump over the drain with a hole in the bottom and caulked to the floor, so if it over flowed the pump would take over; but the manufacturer told me that if the pump wasn't used regularly it would dry out and fail. Any other suggestions?

Pictures of the the drain and the plumbing is attached.

 

I moved your thread to plumbing.
Even though your HVAC drains into it.... it's not an HVAC problem.
More plumbing guys will see the problem in the plumbing forum.

So your thought is that you just have a straight pipe there going down into the ground ?

 

Yes, I have a straight pipe going about 2" into a hole in the ground. Furnace guy said that was normal around here.

Actually I have a (crappy) borescope. Tomorrow I will stick it in to see if there is anything else down there, but I am pretty sure there isn't.

 

I'd be curious to see what happens if you don't drain anything in there for a few days. If it's still wet it's most likely the ground is oversaturated. If it's dry it may be slow draining due to the crap in the A/C condensate and the acid in the furnace condensate has the rock coated or sealed.

 

I live in north Louisiana.

Prior to buying this current home, we owned a home built in the 70's. That HVAC drained into the the drain from the tub, lavatory & kitchen as I understood it. Mine clogged up with gunk over time & I just used a small snake attached to a drill, then used a portable pancake air compressor to blow it out. I just used a rag to wrap around the air line blower & held it down over the opening of the pipe... and let'er rip.

It may not be the way to do it, but that's what my HVAC guy told me to do. Worked for me. I will say that I had a little more room to work with in that drain pipe than you do.
You may need to hear from some of the experts here before trying that approach.

 

It drains, but slowly. With the water turned off to the humidifier and only the water from the furnace going into it, it drains completely between calls for heat. Until a couple days ago it even handled the humidifier, but not now.

My house has two sets of drain tiles that gravity drain, and my yard was not terribly wet. It was other area nearby that had standing water. I don't think the problem is a high water table, but can't be positive.

 

It's hard to believe you don't have a floor drain there instead of just a hole in the floor. I wonder how this house ever passed a final inspection.

 

I'm with Joe. The house is only 15 years old, I would be really surprised if it wasn't actually piped into a drain. I have a house with a floor drain that just goes nowhere, but it was built 100 years ago, certainly not under recent codes.

If it's actually just drains into the ground, I would recommend a condensate pump. I wouldn't want all that extra water going under my slab.
Of course, if it is actually a drain line into an actual drain that has cracked, then cleaning the pipe out is the way to go.

Just my two cents.

 

As hard as it is to believe, it is just a hole in the ground.
If it worked for 15 years, I don't need a condensate pump.

So... back to the original question. If it worked for 15 years, what could have changed and what can I do about it.
What does it mean to be "coated or sealed"? How do I fix that?