Question? Just ask us!
Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair
InspectAPedia ® Home
AIR CONDITIONING & HEAT PUMP SYSTEMS
A/C - HEAT PUMP CONTROLS & SWITCHES
AIR CONDITIONER COMPONENT PARTS
AIR CONDITIONER TYPES, ENERGY SOURCES
AIR FILTER EFFICIENCY
AIR FILTERS, FIBERGLASS PARTICLES
AIR FLOW MEASUREMENT CFM
APPLIANCE DIAGNOSIS & REPAIR
APPLIANCE EFFICIENCY RATINGS
BLOWER DOORS & AIR INFILTRATION
BLOWER FAN CONTINUOUS OPERATION
BLOWER FAN OPERATION & TESTING
BOOKSTORE - Air Conditioning "How To" Books
CAPACITORS for HARD STARTING MOTORS
CLEANING & Legionella BACTERIA
CHINESE DRYWALL HAZARDS
CONDENSATION or SWEATING PIPES, TANKS
DEFINITION of HEATING & COOLING TERMS
DEW POINT CALCULATION for WALLS
DEW POINT TABLE - CONDENSATION POINT GUIDE
DIAGNOSTIC GUIDES A/C / HEAT PUMP
DIAGNOSE & FIX HEATING PROBLEMS-BOILER
DIAGNOSE & FIX HEATING PROBLEMS-FURNACE
DUCTS - Asbestos
DUCT INSULATION, Asbestos Paper
DUCT INSULATION for SOUNDPROOFING
DUCT SYSTEM & DUCT DEFECTS
DUCT SYSTEM NOISES
DUCTS, Asbestos Transite Pipe
DUST, HVAC CONTAMINATION STUDY
ELECTRIC MOTOR OVERLOAD RESET SWITCH
EVAPORATIVE COOLING SYSTEMS
FAN LIMIT SWITCH
GAS EXPOSURE EFFECTS, TOXIC
GAS DETECTION INSTRUMENTS
HEAT LOSS (or GAIN) in buildings
HEAT LOSS (or GAIN) INDICATORS
HEAT LOSS R U & K VALUE CALCULATION
HEATING SMALL LOADS
INSPECTION CHECKLIST - OUTDOOR UNIT
INSPECTION LIMITATIONS, A/C SYSTEMS
LEED GREEN BUILDING CERTIFICATION
LOST COOLING CAPACITY
LOW VOLTAGE TRANSFORMER TEST
MOTOR OVERLOAD RESET SWITCH
MOLD in AIR HANDLERS & DUCT WORK
OPERATING COST, AIR CONDITIONER
OPERATING DEFECTS, AIR CONDITIONING
REPAIR GUIDES A/C / HEAT PUMP
REPAIR & DIAGNOSTIC FAQs for A/C
THERMOSTATS, HEATING / COOLING
THERMOSTATIC EXPANSION VALVES
WATER COOLED AIR CONDITIONERS
WINDOW / WALL AIR CONDITIONERS
WINDOW / WALL A/C SUPPORTS
A/C condensate drain de-clog & cleanout: this how-to article explains procedures for cleaning or de-clogging a sluggish, blocked, or leaky air conditioning or heat pump condensate drain.
Condensate drain cleaning and unclogging tools and methods are reviewed, including simple steps that a homeowner can take to clear a blocked condensate drain at little or no cost.
Green links show where you are. © Copyright 2014 InspectApedia.com, All Rights Reserved.
A clogged condensate drain can cause air conditioner problems or even loss of cooling
Clogged air conditioner condensate drain lines can form another source of air conditioner or heat pump condensate leakage that can in turn lead to hidden water damage or in some locations an indoor mold problem or bacterial contamination.
Our photograph of a nearly full A/C condensate overflow pan (at left) shows what can happen if the primary condensate air conditioner condensate drain line is clogged and worse, the condensate drain overflow pan is also itself clogged and not draining properly. Luckily we caught this attic mold and bacterial pond before it had soaked the ceilings below.
We see air conditioner or heat pump condensate drain lines clogging for several reasons:
Thanks to reader Stuart Oakner for suggesting additional discussion of the Mighty Pump as a less costly way to clear blocked air conditioning or heat pump condensate drains than calling the HVAC service technician.
Green link shows where you are in this article series.
Frequently Asked Questions (FAQs)
Question: AC water clogs - slope is too great on the drain
(June 23, 2011) Ma Neumann said:
A neighbor in my condo tells me that our #1 problem with the AC is water clogs--when the condensate drain's slope is too great, he says, the water rushes down the pipe and clogs up all by itself, sort of like a vacuum. I can't find any references to water clogs on the Internet. Everything I see about clogs uses terms like sludge, dirt, debris--solid material, not vacuums. Please educate me.
Your neighbor's explanation makes no sense to me at all. What clogs A/C condensate lines is typically crud (dust, debris, rust flakes from inside the air handler) that collect in the condensate line trap, or at the condensate drip pan opening that feeds into the condensate line.
Excessive slope is a problem on drain lines on SEWER piping (black water, toilet waste) because if the slope is excessive the water can rush down the drain line leaving solids behind to clog the piping. But on a condensate drain line there is no sewage and no solid waste.
(July 22, 2011) Frank said:
I noticed leakage in my ceiling after a technician rewired my brand new conditioner to run at a higher fan speed which forced more air into my house. Made sense and now feels cooler. a few hours later is when I noticed the water leak. I went into the attic and can see that there is water in the catch tray but the kicker is that there is a small hole a couple of millimeters round at the end of the tray allowing the water to leak out into the insulation down the roof into my plaster ceiling. What in the world is a hole doing in my catch tray?
Question: reader suggests de-clogging condensate drains with a digivac
(Oct 23, 2011) Anonymous said:
try a diyvac wet vac attachment to unclog the drain line .The attachment fits on the wet vac and drain line perfectly and takes a couple of minutes to unclog once vacuum is turned on.
Question: water leaking out onto furnace
(May 31, 2012) jay said:
water is comeing out the top of my ac furnace
Jay, if your unit's condensate drain pan has begun to leak, or if its drain is clogged, those would cause the leakage at the air handler as you described. There should be a removable panel to give view inside the unit to see the condition of the drain pan itself.
Watch out: water leaks onto a heating furnace heat exchanger can cause rust and dangerous heat exchanger leaks - risking cabon monoxide poisoning.
Question: AC condensate drains into a bathroom sink P-Trap
(June 26, 2012) Remo said:
Hello, it looks like my condensate drain goes directly from the ac unit down to a nearby bathroom sink and connect to the p trap. there is no way to pour bleach suck with a wet vac. when the AC kicks on, there is a horrible gorgle sound out of our bathroom sink, how can i fix that?
Remo, it sounds as if the drain tubing needs to be disconnected and cleaned.
Dan, i think you are right, but how do we disconnect it? at what point, mid way? at the AC
I'd start by trying to get inside the air handler (power off) to find the opening into the drain, and to brush clear the trap if one is present.
(July 7, 2012) M12451 said:
My ac runs but water fills up at the bottom where the condensation pump is located, I not sure what do. Can someone with good expertise please advise.
Thanks Not a HOT Summer
But first be sure the condensate pump is plugged in and has electrical power
(July 17, 2012) Ann Borg said:
Our condensate line backed up causing a wet drywall and ceiling....because the builder was too cheap to install an over flow valve. It has been corrected and all of the information on your website was excellent. Thank you.
Ann, sorry to read of the condensate backup - but what "flow valve" are you referring to? It is common to drain condensate by gravity when possible, and it is also not uncommon for the condensate drain trap or line to clog with lint and crud - it's a maintenance item. Can you tell us what valve you mean? Do you mean a condensate overflow tray sensor switch?
(July 27, 2012) Jennifer said:
Hi Our 2 units have only one drain line and it seemns to leak. What is the code that each line shuld have their own independent line?
Jennifer, none that I know about. But the condensate drain does need to be large enough to handle the condensate flow rate without backing up; if your condensate line is leaking I suspect either it is clogged or there are improperly made leaky connections.
Question: who do I call to fix a clogged condensate drain
So if one has this issue, do I call an HVAC technician or a plumber?
Start with your HVAC tech. who may have just the right sized tools to clear the condensate line clog. But some problems such as a clogged condensate line or a broken condensate pump are within the scope of others such as a plumber, handyman, and many homeowners.
Question: condensate water coming out of the ceiling or leaking onto the floor
(Aug 25, 2012) Rich said:
I noticed yesterday that there was water coming through the ceiling and suspected it was the A/C unit. When I got into the attic there was no water in the drip pan or any evidence that it had been wet, and the drain lines were not clogged (did the water/bleach test and drained properly). I opened up the unit which held the refrig evap and that inside drip pan was full and I suspect overflowed into box where the ducting is connected. The liner is soaked as well as one ducting had a puddle of water. This is where the damage to the ceiling came from. Do I have a bad refrig evap unit or bad drip pan inside? My first thoughts were we just recently had a lot of humidity and the drip pan couldnt keep up... Thoughts? Thank you!
(Sept 9, 2012) Samantha said:
I'm noticing water dripping from the bottom of our air handler onto the floor (1st story, closet installation). I'd like to clean out the drain pipe as I'm guessing there is a clog, but there isn't any access point - should I just attach a wet vac to the outside pipe and vacuum it out? Our house came with a heil unit and I can't find anywhere to even open it up to view the drain pan itself.
To answer this we need to look at the drip pan to see if it's clogged, rusted, perforated, leaking, overflowing, or if there is a problem with the condensate drain piping. Start at the unit.
Question: reader suggests other condensate line cleaners
Tom Kolter said:
You should check out the Jones Valve, too, available at Supco and Watso, United Refrigeration and Johnstone, the latter two as "Line Drive".
Questions & answers or comments about how to un-block a clogged A/C or heat pump condensate drain.
Check the FAQs just above, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
Search the InspectApedia website
HTML Comment Box is loading comments...
Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.