Question about Heating & Cooling
The water in my drain pan won't go down the drain pipe while the fan is running, causing the drain pan to overflow when run for long periods. As soon as the fan turns off the water runs down the drain like it is supposed to. I have disconnected the drain pipe to look into the pan and can see the water being held back by the air pressure when the fan is on. As soon as I turn the fan off, the water ran out of the drain hole.
I installed new pvc pipe from the drain pan, all the way to the connection to the main connection and snaked the sewage system 8 months ago. So, I don't think it's a clogged drain.
I baffled as to why the air pressure won't let it drain, because I can feel the air blowing out of the drain hole. Can any explain and tell me what I need to do to fix it?
My A/C unit is located in a hall closet. It's a Lenno gas heater/ Air Conditioning unit that is at least 20 years old.
Posted by mckinney_g on
The drain must have one and only one trap in it. A trap is where the pipe goes up then back down so that water is kept in a section of the pipe - will stop the air from blowing thru the drain and not letting the water drain - may not sound right but it is! I've seen this many times! Drain traps are not understood at all by the HVAC industry.
Posted on May 12, 2009
Tips for a great answer:
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:
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.
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.
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
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.
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.
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!!!
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Thank you, but it does have a trap, and I did cap off the vent pipe on the drain.