Your Condensate Drain

Uh, oh, someone's condensate drain is clogged!

It never ceases to amaze me how people are willfully ignorant about things.   If you live in America, you will own, in your lifetime, maybe a half-dozen each of refrigerators, stoves, microwaves, dishwashers, and the like.   You will probably have a few toilets.   You may own a dozen cars or more.   And you likely will own at least one air conditioner - mostly likely three or four.

Yet most folks have little or no idea how to even operate these appliances, much less how they work.   And in order to do the former, you have to know something about the latter.   It is like trying to drive a 5-speed without understanding what a clutch does.   You'll never get it right, no matter how much you try.

We've been gone a few months and when we came back, I found the condensate drain on our A/C system clogged.   A few pitchers of hot water (and some simple green) later, it is unclogged.   The outside portion got buried with lawn debris, and it backed up and formed a gelatinous goo inside.  It was disgusting.

What is a condensate drain and how does it work?

Well, to understand this, you need to understand something about how A/C systems work.  I'm not asking you to take Thermodynamics and understand Entropy and Enthalpy.  Thermo is a hard course - I took it three times.   Rather, you should understand the basics of how A/C systems work.

Basically, refrigerant (what people call "freon" sometimes) is compressed by a compressor into a liquid.   This liquid is hot because it has been compressed.   An outside coil and fan cool the liquid, which is then passed to an expansion valve.  The expansion valve works like the nozzle of a spray can, and turns the liquid refrigerant into a gas.   This phase change is what causes the cooling effect (just as ice changing phase from solid to liquid is what cools beer in your cooler).    The gas cools when it expands, and this cold gas is passed through another coil inside your house, and a fan blows air over it, which then cools your house.  The gas then goes back to the compressor for another ride around the loop.

OK, so that's A/C for morons.  Not hard stuff.   So where does the condensate line come in?  Well  you have to understand how air works, as well as refrigerant.  And few people do, based on the number of fogged-in cars I see driving around.

Air can hold water basically dissolved in it.  We call this humidity.   Just as you can dissolve sugar in water, you can dissolve water in air.  How much water you can dissolve in air depends on its temperature and pressure.   The colder the air, the less water it can hold - which is why it gets drier in the winter.  When warm, moist air passes over the cold A/C coils in your air conditioner, the water falls out of solution and condenses on the coil surface.  This drips down into a pan and then is drained outside (usually) by a condensate drain.

In a car, the same thing happens.  Problem is, in a car, you can choose "recirculate" or "outside air".  When you do the latter, you are basically trying to air condition planet earth, with predictable results.

You see, any air conditioning system is basically also a de-humidifier.   A de-humidifer is just an A/C unit with both sides in the house.   If you want to "dry out" a house, (or a car) run the A/C.   Funny thing, but people don't get that.  They think if you turn on the heat, it will dry out the house (or a car) but usually all that does is create a hothouse effect.   (Turning on the heat AND the A/C, however, works best.  By heating the air, more water will dissolve (evaporate) in it.  By running the A/C, this water condenses out and drains out the condensate drain.  Just running the heat does nothing, as the water has no place to go!).

Few people understand the science of defrosting.

Getting back to the condensate drain, this tiny pipe can easily clog over time, as mold, mildew and even bacteria colonies grow in it.  Insects may clog it.  Dirt may accumulate.   When this happens, the drip pan in the A/C unit will overflow, usually into your house, possibly ruining your floors or just making a puddle in the basement.

Keeping this line clean and clear is a good idea.   Make sure you know where it exits the house and make sure the yard man does not cover it with lawn clippings (as happened to me).  Run some water through it on occasion (it should be plumbed with an access point to pour water in).   Make sure the outlet of the drain pan does not become clogged.

If all this seems too hard to do (and it is for many folks) then hire an A/C company and sign a service contract.  They will come by your house 2-4 times a year and clean the condensate line, check charge levels, change filters, and clean coils.   It is worth the money, as it avoids problems in advance.

In some installations, a small "condensate pump" may be used to pump the condensate outside or to a drain.   If this pump clogs or fails, it may overflow and leak water all over the place.  Sadly, most installations with condensate pumps are places where a water leak would mean disaster.   So when the pump fails (or the line clogs) you end up having to repair floors or sheetrock or whatever.   If you have a condensate pump, you could check it regularly or get a service contract.

If you don't know whether you have a condensate pump or not, maybe you need to get a service contract.

UPDATE:  Some condensate pumps have a float valve which will shut off the air conditioner if the pump sump overfills.  This prevents the spillage of water and ruining your floors.  But it does mean, to many, that their air conditioner has "mysteriously" stopped working.  Again, keep those condensate lines clear and avoid these problems!  If you can't do this yourself, get a service contract.  I do both.