Just recently I heard of three incidences where the AC condensate line broke and the water causes major damage. In all three incidences the air-handler/evaporator coil was installed in the attic and 3/4" schedule 40 PVC pipe was used for the condensate line. In each case the residents turned on the AC for the first time of the season and didn't realize they had a problem until days later when condensate finally seeped through the ceiling and down the inside of walls and soaked into hardwood floors causing them to buckle. It looks like someone hit the PVC pipe with a sledge hammer making it shatter, it wasn't just cracked. Now I'm paranoid about my system since my evaporator coil is also in the attic. Here in PA we can have some very cold winters and very hot summers. I'm thinking maybe it's the wide variation in attic temperature that's causing the PVC pipe to break?? Is there anything better that they currently use for condensate lines, i.e. like cu or Pex? Maybe I should replace my condensate lines? Any insight would be much appreciated!
Bill

PVC is very fragile. I would assume that the line plugged and then froze the water inside. PEX would be a fairly easy conversion, there is no pressure on the line so a barbed fitting should work. You may be able to snake PEX through the existing PVC since 3/4 PEX is smaller OD than the 3/4 PVC ID. Newer codes require attic units to have a visible drain from a pan, mine is in the soffit over the window.

Thanks for the quick response! I didn't realize PVC is fragile. In my limited experience I find it very flexible and forgiving. I don't know if those three condensate lines were plugged, causing the problems. If they were plugged it would have been from last season but the problem in each case only started at the very beginning of this season. No one had any condensate running down interior walls last year and none of those systems had a pan under the unit with a secondary drain line. They all had only one condensate line... I have a pan and second line in case of a clog. I'm thinking the PVC failed due to a combination of age and the year after year of thermal cycling. I'd really like to verify that somehow. Do HVAC people routinely replace PVC condensate lines after a period? My PVC condensate lines are easy to access in my attic so I'd simply rip them out and replace them with new PVC or Pex. They don't make 3/4" DWV cu or I'd use that and using type M is just too expensive.Bill

With easy access use PEX. Not sure of age, we sold a house last week, built in 1974 and it still had the original 3/4" gravity PVC line. There is little thermal cycling in a condensate line unless you consider ambient temps, then there is possibly a 150* change.