HVAC – Cleaning Your Condensate Drain

You probably read my article on “Is your Air Conditioner running Efficiently“, there are a lot of good tips in that post as we near the air conditioning season. In this post I want to highlight the condensate drain (another one of those items that gets little respect or notice until it’s not working properly).

Looking at the picture with the blue box knife you will see a piece of 3/4 copper with all but about 1/4 inch opening left. This is what I found today as I replaced a condensate drain. I would have never figured this!! As with many HVAC installations, units may be changed out every 10 years or so, but how often is the condensate drain replaced or inspected? Granted, this will not impede the unit from making cold air, but it may leave an ugly damp spot on the ceiling or floor (depending on the location of the HVAC).  As it can back up and overflow.


HOW DOES A CONDENSATE DRAIN WORK: Lets first start by understanding  what the condensate drain does. In the process of the cooling the house, the evaporator coil inside the air handler unit (located in a closet, attic or basement) operates at a temperature that creates condensation on the cooling coil. The collected water from this process  has to drain off. The water drips off the evaporator and is  expelled through a drain pipe. Based on gravity and slope, the water is either released outside the house or into the sanitary drain pipes. This drain tube must stay clean of debris, otherwise it can back up and cause water to drain into the house damaging sheetrock and possibly the building structure. They only drain when the unit is running in AC mode. Visually seeing water dripping is not a good enough inspection as it could still be backed up.


Visually inspect the condensate drain for all the parts mentioned in this picture. Pouring a vinegar in the VENT and the pan will allow you to look for leaks and the rate of flow. Both locations should drain in a few seconds.

  • VENT: Should be open and clear.
  • PAN DRAIN: Should be open and clear. Should exit out of the house where visible. If you see water dripping from this drain pipe (at its exit), the primary condensate drain is probably stopped up.
  • DRAIN PAN: Resides under the HVAC unit and should be clear of debris and free of water. Rusted pans should be replaced. Collected water in this pan is an indication there may be a drain flow stoppage of the primary drain.
  • PRIMARY & PAN DRAIN: Both should have a slight downward slope to its destination. This will ensure the water can flow freely out of the house.

HOW TO CLEAN A CONDENSATE DRAIN: If the drain has never been cleaned, it would be best to use a Wet/Dry vacuum cleaner to attach to the pipe (at the end, outside the house) to suck out all the debris. Seal the vacuum cleaner hose to the drain pipe (furthest from the HVAC). Run the vacuum for about 5-10 minutes. In really bad cases, you may need to pour some vinegar down the drain to pull the gunk through the pipe while the vacuum is running. If necessary, you may need to repeat it until it shows to be running free and clear.Once you know it is clear pour a a gallon of vinegar down the drain once a year. That should keep it in good shape.


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