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Discussion Starter · #1 ·
Hello
Is there a need for a p-trap or j-trap or whatever it's called in the pvc drain tubes of my ac (see picture)?
Is it there to trap smells from coming in, like with water supply lines?
I just picture a lot of that gooey mold accumulating in there despite periodic bleach pourings in the tube.
Thank you
633066
 

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Yes you need a trap. If it is a long line then you should also have a vent after the trap on the drain side, not the AC unit side.
 

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Discussion Starter · #4 ·
Thank you @chandler48

Yes you need a trap. If it is a long line then you should also have a vent after the trap on the drain side, not the AC unit side.
Thank you as well. Can you elaborate a bit?
To the right (before) my trap is a vertical tube that ends with a T-fitting that can be uncovered at the top; the perpendicular hole on the T attaches to the drain line out of the ac unit.
 

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Naildriver
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The vertical pipe is acting as a vent, and as a point that you can pour bleach down to clean out the trap. Dual function. That is why the tee is not glued on.
 

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Thank you @chandler48


Thank you as well. Can you elaborate a bit?
To the right (before) my trap is a vertical tube that ends with a T-fitting that can be uncovered at the top; the perpendicular hole on the T attaches to the drain line out of the ac unit.
That’s the wrong location for a vent. It’s for clean out only. Make sure you cap it off again after you clean the line.

I should specify, you only need a trap if the line is on the negative pressure side of the blower. If the AC coil is on the positive side of the blower then you don’t need a trap.

The trap is not there for sewer gasses, it is there to provide a liquid seal so that air does not get pulled through the trap backwards. If air gets pulled through backwards then it can stop the condensate from draining and cause the pan to overflow. The required depth of the trap depends on how much negative pressure the system runs at.

Cleaning the trap is a maintenance task. I don’t suggest pouring bleach through your pipes. It’s very hard on metal pipes if you have them, because of how corrosive it is. Just flush it out with water periodically.
 

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Discussion Starter · #7 ·
I should specify, you only need a trap if the line is on the negative pressure side of the blower. If the AC coil is on the positive side of the blower then you don’t need a trap.

The trap is not there for sewer gasses, it is there to provide a liquid seal so that air does not get pulled through the trap backwards. If air gets pulled through backwards then it can stop the condensate from draining and cause the pan to overflow. The required depth of the trap depends on how much negative pressure the system runs at.

Cleaning the trap is a maintenance task. I don’t suggest pouring bleach through your pipes. It’s very hard on metal pipes if you have them, because of how corrosive it is. Just flush it out with water periodically.
Thanks again
How do I know if my coil is on the positive or negative side of the blower?
As I face my blower unit, the A-shaped coils are toward the left and the drain holes are on the bottom right corner of the blower.
 

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Thanks again
How do I know if my coil is on the positive or negative side of the blower?
As I face my blower unit, the A-shaped coils are toward the left and the drain holes are on the bottom right corner of the blower.
If the coil is on the filter side of the blower motor then it is on the negative pressure side (return air side), if it is on the supply air side of the motor then it is on the positive pressure side.

If the trap is dry then you may be able to feel the air coming out of the drain line when the fan is running if it’s on the positive pressure side.

If the trap is dry, then a single ply of toilet paper may suck up to the drain line if the drain is on the negative pressure side.

Both of those last two tests won’t work if there is water in the p trap or if the cap is off of the tee at the air handler drain line connection.
 

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Discussion Starter · #9 ·
That's what the drain pipe looked like before I washed it out. Yuk.
I was getting water pooling in the floating safety sensor, so i had to cut to take a look.

633092
 

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That's what the drain pipe looked like before I washed it out. Yuk.
I was getting water pooling in the floating safety sensor, so i had to cut to take a look.

View attachment 633092
Yep. Common issue. If you have one, use a shop vacuum to suck from the drain line outlet. It’s the easiest way to clean it. It helps if there is water behind it so the velocity of the water will clear out the debris.
 

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Discussion Starter · #11 ·
Yep. Common issue. If you have one, use a shop vacuum to suck from the drain line outlet. It’s the easiest way to clean it. It helps if there is water behind it so the velocity of the water will clear out the debris.
Yes sir. But since all the pvc was glued, I could not get to that tube in the picture.
I cut it and rebuilt it as it was but without using cement. Now I can take it apart and clean. After all, it's not pressurized water and just a trickle, so there's no need to use cement.
 

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Yes sir. But since all the pvc was glued, I could not get to that tube in the picture.
I cut it and rebuilt it as it was but without using cement. Now I can take it apart and clean. After all, it's not pressurized water and just a trickle, so there's no need to use cement.
Good job! If it’s in an area where it won’t get bumped or cause damage if it leaks then that should be fine. I will recommend glueing all connections that will have standing water and leaving only the two on either side of the trap unglued so that you can remove it as an assembly when you clean it. That will reduce your chance for leaks and, provided you have the movement in the pipes to remove it like that, it will make removal and reinstallation easier in the future.

90% of the time it won’t leak when assembled without glue. If you find that it does, or if damage will result if it leaks, then you can get PVC Unions that work really well for adding serviceability. I typically install one before and one after the p trap and vent assembly when I do the install or if I have to rebuild them for customers.
 

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Discussion Starter · #13 ·
90% of the time it won’t leak when assembled without glue. If you find that it does, or if damage will result if it leaks, then you can get PVC Unions that work really well for adding serviceability. I typically install one before and one after the p trap and vent assembly when I do the install or if I have to rebuild them for customers.
thanks again Aze.. I've been looking to see if some sort of elbow exists that has one side that slides into the inside diameter of a 3/4 pvc pipe, but I don't think that it exists; I found a 3/4 street elbow that has a smaller-looking side, but I haven't had an opportunity to go to HD thanks to hurricane Eta.
If I dont find such an elbow, I will take your advice to glue most of the piping but leaving 2 loose ends for removal and cleaning.

In an earlier reply you mentioned that I should have a vent AFTER the trap, but I see that I don't. Is that a big deal? I will describe what I have since it won't fit in 1 picture and most of the piping is covered by shelves and other things.
The AC drain comes out of the handler as a small 3/4 pvc pipe followed by:
Elbow
Straight tube slopping downward and wrapped in foam into a T
The T has an open removable top and a downward pipe into an elbow
Elbow followed by the trap you saw in the picture.
From trap, 3 foot straight pipe towards wall.
Elbow followed by straight 20 ft run into an elbow
Elbow into block that drains outside

I periodically pour bleach into the top of the T with the hope that it dissolves and gets rid of the muck build up, but I doubt that it will do anything. I wish that 20ft run was shorter and more accessible, but that's what I inherited.
 

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thanks again Aze.. I've been looking to see if some sort of elbow exists that has one side that slides into the inside diameter of a 3/4 pvc pipe, but I don't think that it exists; I found a 3/4 street elbow that has a smaller-looking side, but I haven't had an opportunity to go to HD thanks to hurricane Eta.
If I dont find such an elbow, I will take your advice to glue most of the piping but leaving 2 loose ends for removal and cleaning.

In an earlier reply you mentioned that I should have a vent AFTER the trap, but I see that I don't. Is that a big deal? I will describe what I have since it won't fit in 1 picture and most of the piping is covered by shelves and other things.
The AC drain comes out of the handler as a small 3/4 pvc pipe followed by:
Elbow
Straight tube slopping downward and wrapped in foam into a T
The T has an open removable top and a downward pipe into an elbow
Elbow followed by the trap you saw in the picture.
From trap, 3 foot straight pipe towards wall.
Elbow followed by straight 20 ft run into an elbow
Elbow into block that drains outside

I periodically pour bleach into the top of the T with the hope that it dissolves and gets rid of the muck build up, but I doubt that it will do anything. I wish that 20ft run was shorter and more accessible, but that's what I inherited.
20’ is a long run to have without having a vent. That said, sounds like it has never caused problems without one... unless the plugged up drain was actually not plugged up but instead simply not draining because it was missing the vent. The picture you showed didn’t indicate a completely blocked drain. I recommend installing a vent. It’s good practice to have the top of the vent above the height of the evaporator drain pan. That added height will insure a blockage will cause a backup into the evaporator pan instead of the floor.

I’m not sure why you want s fitting to fit inside the 3/4” pvc. That would be very restrictive and be prone to blockages.

You can use clear vinyl tube and gear camps to make a connection. The tube slips over the outside of the PVC pipe. The benefit with this over a coupling is that it can slide back and forth along the pipe so you can remove the trap without having to move the rest of the drain line. Don’t undersize the tube or it won’t want to slide next year when you go to use it... if you need it again. Wet/Dry Shop vac solution may take care of all your future problems when it’s clogged and a vent should fix the issue if it’s caused by that probability.

Sounds like the bleach hasn’t worked for you in the past this far, and it’s hard on the pipes. Best to stay away from that practice.
 

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Discussion Starter · #15 ·
633148
633149
@azeotrope
Thanks again. After 9 years in this house and with no issues, you'd think that it was done correctly when the ac was installed in 2011.
I did some research, and I learned that I have a negative pressure system - the blower fan sits atop the coils.
For peace of mind, and your opinion, I'll attach pictures of what I have. I appreciate your opinion on what you see.
The downward tube wrapped in black foam is unglued at both ends.

I also learned that the 14 foot straight run is not so straight. It has to make a small and 90 degree bend, and I hope that it drains properly Why such a long run if that outside wall is block and easy to penetrate???
 

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View attachment 633148 View attachment 633149 @azeotrope
Thanks again. After 9 years in this house and with no issues, you'd think that it was done correctly when the ac was installed in 2011.
I did some research, and I learned that I have a negative pressure system - the blower fan sits atop the coils.
For peace of mind, and your opinion, I'll attach pictures of what I have. I appreciate your opinion on what you see.
The downward tube wrapped in black foam is unglued at both ends.

I also learned that the 14 foot straight run is not so straight. It has to make a small and 90 degree bend, and I hope that it drains properly Why such a long run if that outside wall is block and easy to penetrate???
Maybe I’m mistaken, I thought this plugging up was a common issue on your system. You should only have to clean out the trap once a year at most.

You could install a vent after the 90 at the wall (downstream of your trap). Run the vent up the wall to the height required and fasten it so it doesn’t get bumped. If you haven’t had any issues then sometimes it’s just best to leave it. I’m not sure how they made their drain connection so installing a vent now could allow sewer gases to enter the space. Ideally they would not have connected it that way but without knowing for sure then I have to assume there is a possibility... Could be opening a can of worms.
 

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At this point it seems all you need is a way to service it. If the top horizontal pipe is removable then that gives you a good access point to blow air through the trap rather than suck it through. That will work too. Looks like that will be an adequate service location
 

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Discussion Starter · #18 ·
At this point it seems all you need is a way to service it. If the top horizontal pipe is removable then that gives you a good access point to blow air through the trap rather than suck it through. That will work too. Looks like that will be an adequate service location
Aze, you are correct.
I didn't mean to imply that I have constant blockage of the pipes. I simply noticed the thermostat turn off, saw the float drain cup full, and reacted to that. So, all in all, it has been draining and it simply accumulated over a long time.
We will not open any cans of worms, as you mentioned, and I'll leave it as it is with the now serviceable pipe.

What concerns me is that under that downward pipe I've been feeling the slightest of water coming out of the elbow on 1 end and the coupling at the other. Those slight water leaks will become a bigger problem with time - we all know what water does. That's why I was asking for an elbow that fits into the pipe so that the water has no way to leak. I will just have to make sure that the joints at those 2 points are as tight as possible and that the pipe goes in all the way into the coupling and the elbow.

A million thanks for your time.
 

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Discussion Starter · #19 ·
@azeotrope and perhaps others
I revive this thread after a recent cleaning of my coils which was a success.
I attached a sketch of my AC drain line that runs along the left wall of my garage, and eventually drains to the outside (colored in red). Unfortunately, that outside hole and pipe were covered with concrete which makes it inaccesible. More importantly, it is draining right outside the garage's concrete blocks, so the water is going right to the foundation of the house. The area inside the garage marked with X's, smells very humid because that AC drain water is accumulating in that same area since no proper drainage was put in when the concrete was poured.

So, I'd like to redesign my drain line for the purposes of:
1) Making it accessible for servicing (suction).
2) Sending that drainage water away from the house as much as possible.

My initial thought for the drainline is to (refer to attached drawing):
1) Drill an new hole on the concrete blocks
2) Attach an elbow and pvc to the existing run and take it outside (colored in blue)
3) Somehow put that blue pipe to drain into the rain gutter.
4) The rain gutter will take it away from the foundation, BUT on to the driveway. This implies that water will be pouring onto the driveway constantly. It received sun most of the day, but that might turn messy and ugly with time.

What do you think of my proposed solution? I really don't have any other choice.
And since I will be getting pipe and cutting, should I redesign my existing piping inside the garage? It may function properly, but I imagine that it hasn't been properly cleaned or vacuumed in many years, so laying new pipe allows me to install it clean.
Thank you.
654717
 

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Not understanding the reasoning behind boring a hole through a normally non leaking wall to put a pipe.

And water "drips" out, not "pours" out. I don't think you will notice it and it should evaporate rather quickly.
 
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