It could be a leaking water heater.. if it's a heavy amount of water as you suggest that would be my guess. While AC's can produce alot of condensate this is December. Not likely to be the AC.

If he doesn't fix that or any problem with water leaks it will only grow to a bigger costlier problem. Never worth ignoring "any" leaking water type issues.

When you own a home, it is your biggest expense... but also your biggest asset especially recently as all home values are up, up, up in nearly all markets. He doesn't want to become a victim of the "ugly home people" does he? (pennies on the dollar)

Skimp somewhere else... protection of your biggest asset is worth it in the long run.

Although a leaking hot water heater would explain it, his water heater is working fine. It is in the garage with no issues. The problem he has is only when the AC turns on. If it is mild outside they won't turn. It on and the curb is dry. During the summer/fall it was on for so long that there was an algae trail down the entire length of the curb.

Ok I've used 1 of my 3 guesses,here's the secound of my allotment. The ac return air has a huge leak pulling hot humid air from attic. Along with repairing air leak,the evap coils will need to be cleaned. Oh what the hey,may as well go for broke and take my third shot. The humidifyer is squirting 10x water as it should and excess is falling in condensate drain. I have ever reason to expect you will tell us when and if we make the right guess,,,right,,,,,,,right HU-268695074 ?????

I would think that their water bill would be astronomical if the humidifier was dumping the water at the rate I am seeing? Let me see if I can get a picture of the curb to show you. It literally looks like someone left the hose on. It is dark right now but tomorrow morning I will get one. There are ripples in the stream on the curb, so much water.

It would be better to take a picture at the attic source.

It's not particularly humid here in NC right now so you can pretty much eliminate condensate from dehumidification. That leaves a water leak somewhere. Humidifier (unlikely in NC)? Water heater? Washing machine? Ice maker?

EDIT: A condensing furnace can put out over a gallon an hour.

"It woulmake'sd be better to take a picture at the attic source".

Rotflmao,I'm not laughing at you,I'm laughing with you Stax. Considering the amount of water OP said has been running accross the yard,down the curb and into storm drain for months,your observation is so logical it make's us wonder why they sat there watching without as much as asking a neighborhood kid to go up there and tell them what he seen. That picture business gave me a chuckle but then came the suggestion it might be the washing machine or ice maker and I couldn't control myself. Picture this if you can. Homeowner has been trudging up to the attic for ice and do the laundry for months and never thought to look and listen for the source of water.

LOL.

Yeah take a picture of the pipe the water is coming from at the point in which it comes out of the house. That pipe (what ever, where ever it is... would provide clues.)

I'm pretty sure everyone here knows what water looks like at the curb.

The water bill grows over time, people just keep paying it... ironically enough. Until one day... (that's how the story goes most of the time.)

what kind (type) of heating system? Does the house have a pool?

AC only makes condensate when it is running. It's December 7th today. While we are still using AC where I live, it isn't going to run long enough durring this time to create the kind of water you're telling us it is.

If I am wrong, you should be talking to Ripley's (believe it or not). LOL.

Also in terms of water heaters, it's not uncommon for *some* homes to have more than one. You'd be surprised to find out home owners are often puzzled to find this info out even after living in a home for a decade or more.