The first in our series, this post as well as those that preceded it, are intended to help homeowners maintain their home by addressing some of the most common, often easy to address, issues.

Air conditioning here in the Piedmont of North Carolina is considered essential.  And rightly so.  From May through September, daily temperatures average above 80°.  July and August average right at 90°.  Raleigh also deals with high humidity – the amount of moisture present in the air (our yearly average is 70%).  Humidity changes the ‘real feel’ temperature and can make a 90° day feel like 100°.   

Most air conditioning units we see operate correctly. But one by-product of a correctly operating unit can cause damage to other parts of your house – condensation coming from the unit.

On a hot day, a properly working unit can produce as much as 20 gallons of water from condensation.  Where does this water/condensation come from?  Think about a glass of iced tea when you are sitting outside on a hot day.  Condensation (water droplets) form on the glass.  That condensation is caused by a warm air mass, filled with moisture, meeting a cold surface.  That moisture condenses – is pulled – out of the air and onto the cold glass.

An air conditioning unit works in a similar way.  Inside the unit are coils – metal tubes filled with cold refrigerant.  The unit pulls air across these refrigerant lines to cool the air.  At the same time, the unit pulls humidity out of the air as the air is pulled across the coils.  Just like that glass of iced tea, the coils accumulate condensation.  This condensation is funneled into a drain, which is then piped outside the house. 

So, what’s the problem if the unit works correctly?  It’s a matter of where that condensation goes.  In most homes, the condensation is piped out to the exterior of the home.  Usually, we see a PVC pipe exiting the home foundation near the exterior AC unit.  On a hot day, this PVC pipe drips water continuously – once again, up to 20 gallons a day – right next to the foundation.   

What can happen because of this? One result can be foundation damage.  The soil here is mostly clay.  When clay gets wets it expands and, if wet enough, turns to mud, which is damaging to a foundation.  Expansion or soft soil will put additional pressure on the foundation, which can cause uplift or sinking of the foundation.  This process can lead to foundation cracks, which can then negatively affect the structure above (walls, floors, etc.).  

This drainage can also lead to moisture problems in a crawl space or basement.  Over time, the water from the PVC pipe can seep down and migrate into the walls or under the foundation.  This can show as efflorescence in a crawl space or wall issues (peeling paint, etc.) in a basement.  Moisture can lead to mold or other organic growth problems.

Outside the house, the drainage can cause erosion problems.  One serious area is under the pad the AC unit sits on – remember that most condensation drain lines exit the home near the exterior AC unit.  Erosion under this pad can cause the unit to lean, and an un-level unit can lead to damage to the unit or refrigerant lines.

The answer?  Simple – extend the condensation drain line away from the foundation far enough so that any water from the line cannot return to the foundation.  (A side note:  it should also not be buried.  You want to see the open end. If the water is not dripping out on a hot day, there is another problem – usually a clogged line.)  A qualified plumber or handyman can extend the condensation line.