Tip & How-To about Heating & Cooling

How to Clean Out a Clogged Drain Line on Your A/C System

It is very common for the drain line on your A/C system to get clogged from time to time. This will cause the water to build up in the drain pan located directly under the evaporator coil. This water will eventually spill over and leak through a small overflow hole in the pan and/or directly into your a/c system and onto the floor or, worse yet, through your ceiling if your unit is located upstairs or in the attic.
It is typically fairly simple to clean out the drain. One of the easiest ways is with the use of a Wet/Dry vacuum.....the stronger the better. If you know where the drain line terminates outside the house, place the end of your vacuum hose over the drain. To achieve a stronger vacuum, I recommend placing a large plastic bag or a wet rag around the end of the hose attached to your drain.....this will block off the air gaps.
Another way to clean out your drain is by cutting the drain line no closer than 4" from the drain pan......preferrably between the trap and the unit. Do not cut close to any fitting as you will need at least an inch of pipe to put on a coupling or rubber hose. Prior to cutting your pipe, I recommend you identify what type of pipe you have including Outer Diameter of the pipe and make sure you can get the fittings or rubber tubing you will need to put it all back together. Okay, now you can cut the pipe, place a coupling or rubber hose over the end that is leading to the outside, place your garden hose nozzle in the fitting/hose and blast out the pipe. I suggest using a rag to wrap around the area of the nozzle and fitting/hose as you will get some dripping and possible some splashing. If the drain is clogged, you will feel strong back pressure as you spray, but once the clog breaks free, you will feel the water flowing freely through the pipe with little back pressure. Now you can use either a fitting (coupling & glue) or you can put it back together using a rubber hose and some hose clamps. Make sure your fittings are tight so as not to create a water leak in your house. The advantage to using a rubber hose is the ease of which you can access your drain again in the future. The disadvantage is the potential for leakage if you use a hose that is too large or fail to properly tighten the hose clamps.
You can always try to snake out the drain, but I find this to be the most cumbersome and difficult way to clear a drain..........Personally, I have snaked out a drain only about 3 times in my 20 years in the field. And of those 3 times, they were the most stubborn of all blockages.
I've seen some people make the mistake of removing the drain trap from their system believing that they can eliminate future cleanouts by removing the most common location of blockages. Do not make this mistake. The drain trap prevents air from being sucked into your drain (and your a/c) from the outside through the drain line. Also, in many cases, without the drain trap, the water will not be able to drain due to the strong suction of air being drawn through the pipe.

Please let us know if you found this tip to be very helpful to you as you take on clearing that clogged air conditioning drain line yourself. You can do it! :-)
Don't forget the most important component of your A/C - The Air Filter! Keep it in Place and Keep it Clean! :-)

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drain inside house from a c is over flowing.central air



I am a certified HVAC Technician. I have worked in the field since 1996. I have seen this hundreds of times, if not a thousand times, in the past. Every central air conditioning and heat pump system comes with TWO drain pans, The MAIN drain pan is located within the AIR HANDLER (blower) UNIT, while the EMERGENCY DRAIN PAN is extremely LARGE and sits under the ENTIRE AIR HANDLER (blower) UNIT. The ONLY time water will be INSIDE an EMERGENCY DRAIN PAN is when the MAIN DRAIN PAN condensate drain line is CLOGGED, causing the MAIN DRAIN PAN to overflow. What causes the drains pans OR the drain lines to become clogged is slime and scale from the condensate water as well as debris from within the attic that may have either been blown by the air or may have simply have fallen into the emergency drain pan; or some insects from the out of doors have traveled up into the PVC Drain line and built a nest on the downward side of the P-trap. The P-trap is designed to prevent critters from entering your home through the PVC drain lines. Most CLOGS occur at the P-TRAP location.

The BEST thing to do is:


1. Locate the WHITE PVC drain pipe outside your house and ensure there is NO water draining from it.

2. Locate the same WHITE PVC drain pipe inside your house. You should notice a "TEE" where two WHITE PVC drain pipes merge into ONE WHITE PVC drain pipe.


Follow the below steps, in the order shown:


A. FIRST, find another person to act as your second set of eyes at the end of the WHITE PVC Drain Line that is located outside of your home. That person will be looking for water or debris to EXIT the end of that WHITE PVC DRAIN LINE.


B. SECONDLY, locate the WHITE PVC "P-TRAP" inside your house. It is normally located within a couple to three feet of your indoor air handing (blower) unit.

C. THIRDLY, very gently lift the entire WHITE PVC drain line up in the air as high as you can without breaking it, and slam it down onto the rafters or attic floor or garage floor. You are attempting to dislodge the CLOG within the drain pipe WITHOUT having to actually CUT the PVC and without damaging or breaking the WHITE PVC. Depending on how old the system is, it may or may not be brittle; and it may not take much to damage or break the PVC, which will cause leaks. So, be very careful at this point.


D. Ask the person outside if anything has started to EXIT. You can ALSO usually hear water start to drain if you put your ear up to the drain line. If the person said "NO"and if you don't see the water level getting LOWER in the EMERGENCY drain pan, then REPEAT step "C" above.

E. If the person informs you that there IS water now starting to exit the WHITE PVC DRAIN PIPE, you should then wait until all water has drained from the EMERGENCY DRAIN PAN; and then pour at least 1 quart of BLEACH down that drain, from the EMERGENCY DRAIN PAN exit. The BLEACH will further clear out any SLIME which may be remaining within the "P-TRAP" and will also CLEAN OUT and DISINFECT that drain line.

If the above steps do NOT work for you, then prepare to go into the next LOGICAL phase of your attack. Please NOTE: I am limited to 10,000 characters in my response, so I'll repost additional STEPS in another RESPONSE. Good Luck!!!

Sep 05, 2012 | Goodman CLQ36AR49 Air Conditioner

1 Answer

Water building up in drain pan.


Is this a split unit? The drain line is probably clogged. If you have a shop vac you can use it on the drain line outside and clear the clog or maybe use something like drano. A little Clorox added to the drain pan every now and then will help keep the drain line from getting clogged. (Just a couple tablespoons)

Sep 01, 2010 | Heating & Cooling

1 Answer

Water in the drip pan- what is causing it?


I assume you are talking about the indoor unit. One function of the a/c system is to dehumidify the air. Condensation forms on the cooling coil and runs to the drip pan. There should be a drain line on the drip pan that drains the pan outside. These sometimes become clogged causing the water level in the pan to rise. Try some mild drain cleaner to open the line. Hope this helps. Let me know what you find.

May 21, 2010 | Carrier 38CKC036 Air Conditioner

2 Answers

Air Conditioner (RUUD model: UBHC-14J06NFD) is leaking water from bottom. It is causing a major puddle in Air Intake area.


The condensate drain line/pan is clogged causing the condensation to overflow the pan.

The easy way to fix that is attatch a powerfull wet/dry shop vac to the end of the drain line and such out whatever is causiing the clog. Also take off the panel to the evaporator coil and clean out the pan with the shop vac.

To double check that the clog has been removed, pour a gallon or two of water into the pan and ensure that it is draining properly.

Oct 11, 2009 | Heating & Cooling

1 Answer

Kenmore # 63142 Fridge -- Water in Freezer


If water drains out, then there is always a blockage somewhere on drain line.

Defrost the unit completely to get rid of ice building inside drain lines.

If that does not work , then the drain line must be unlocked using a flexible shaft.

Apr 04, 2009 | Kenmore 63142 / 63144 Top Freezer...

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