On the home furnace it has an A/C water drain PVC tube. They have a little bend in it up by the furnace to sort of act like a water trap ? Well I forgot to add bleach to this for awhile and it got slimed up and plugged up and got a mini flood in the basement. Is this trap like feature really necessary for these ? Or can I do away with it in hopes it will be less likely to plug in the future.
- Thread starter Mike M
- Start date
pete black
Well-known Member
Essentially an insect barrier.
Angle Iron
Member
t will form a vacuum on the drain like a venture effect without the trap. This will cause it to hold water in the drain pan and if the unit doesn't cycle pretty often to break the vacum and allow it to drain it will overflow.
Steve@Advance
Well-known Member
It needs the trap for several reasons. Especially if it drains into the sewer, to prevent sewer gas from being drawn into the house. You might consider adapting a larger trap if there is room, like a 1 1/4" that would be used under a bathroom sink. Those unscrew to be cleaned.
But most important is prevention! Every ac unit should be equipped with one of these! Especially those installed in the attic or over a carpet or hard wood floor.
https://youtu.be/L7V6iq7qMSI
It is a simple float switch connected to the thermostat circuit that stops the compressor before the pan overflows.
But most important is prevention! Every ac unit should be equipped with one of these! Especially those installed in the attic or over a carpet or hard wood floor.
https://youtu.be/L7V6iq7qMSI
It is a simple float switch connected to the thermostat circuit that stops the compressor before the pan overflows.
Steve@Advance
Well-known Member
Well, I thought the video would show how to install it...
It simply screws into the overflow port of the condensate pan. Water gets too high, it shuts off the unit.
It simply screws into the overflow port of the condensate pan. Water gets too high, it shuts off the unit.
The drain tube out of the evaporator pan has a slight positive or negative static air pressure on it from the fan, depending upon how the air handler is set up.
The little "trap" holds enough water to block the flow of cooled air OUT of the unit through the drain tube, or the flow of surrounding air non-air conditioned INTO the drain tube, yet allows water to drain.
As to sewer gas, one would expect to see an air gap between the drain tube and a floor drain or other sewer intake... either of which would have it's own septic trap separate of the trap on the AC drain tube.
The little "trap" holds enough water to block the flow of cooled air OUT of the unit through the drain tube, or the flow of surrounding air non-air conditioned INTO the drain tube, yet allows water to drain.
As to sewer gas, one would expect to see an air gap between the drain tube and a floor drain or other sewer intake... either of which would have it's own septic trap separate of the trap on the AC drain tube.
Typical positive pressure coils (resi split systems),
don't "need" a trap. The manufacturer suggests it, the AHJ
has the final say (when inspected) and it often gets removed the first time it plugs,
problem solved. No it doesn't "need" it,
just another maintenance problem. It should have a vent-a tee & short
nipple-, the trap would be at the drain it runs into, floor, sink, whatever.
We have gone to 3/4 pvc, in the past sometimes 1/2 was used, but
I have less problems w/ 3/4. If I have a 1/2" problem child, I redrain
it 3/4.
don't "need" a trap. The manufacturer suggests it, the AHJ
has the final say (when inspected) and it often gets removed the first time it plugs,
problem solved. No it doesn't "need" it,
just another maintenance problem. It should have a vent-a tee & short
nipple-, the trap would be at the drain it runs into, floor, sink, whatever.
We have gone to 3/4 pvc, in the past sometimes 1/2 was used, but
I have less problems w/ 3/4. If I have a 1/2" problem child, I redrain
it 3/4.
Bob has it right below. Purpose of trap in condensate drain like that is to prevent flow of air either into or out of the AHU/furnace. Depth of trap is determined by the fan static pressure, too shallow and the fan can either blow or suck the trap dry. Sewer gas is not an issue since a drain of this type should not be directly connected to a sewer. The trap also needs to be a prescribed distance below the unit again depending on fan pressure. Link below gives a pretty quick overview for those really interested.
Condensate Traps
Condensate Traps
Pete in Holland MI
Member
My A/C coil in my furnace has a drain that goes to a floor drain. No trap. There is also cool air being blown into the drain. The trap may prevent this small leak.
Pete
Pete
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