A/C leaking- no clog in condensate line or overflowing drip pan

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  #1  
Old 06-07-16, 06:25 AM
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A/C leaking- no clog in condensate line or overflowing drip pan

For the past couple of days we have had water intermittently seaping out from under our A/C unit. See photo. We completely cleared the condensate line and made sure there is no clog and we opened up the unit and the drip pan isn't overflowing or leaking. We also changed the filter. Is there anything else that would cause water to leak out from under the unit? If you see the photo it is seeping out from where the dry wall meets the concrete.

Thank you in advance.

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Last edited by mickapoo; 06-07-16 at 06:43 AM.
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Old 06-07-16, 06:30 AM
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What other water source is nearby ,toilet ,washing machine,sink?
 
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Old 06-07-16, 06:39 AM
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There is a hot water heater to the left of it, but we checked that and there is no leak around or under it. The only other thing relatively close by might be the refrigerator, but I pulled that out earlier this morning and I didn't see anything leaking behind it.
 
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Old 06-07-16, 07:50 AM
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I do not see a p-trap...

That unit flows up, correct? If its a downflow, its ok, but if that is a more typical upflow, you need a trap(unless its out of view).

A p-trap performs an important function in an AC unit.

Is it extremely humid where you are right now?

If you don't have a trap, and your filter(pre coil) is dirty(check that), the drain will draw more air into the unit(through condensate piping), causing the water to sometimes not drain. The trap fills, and cuts off that air flow.

If you have no trap I would venture that is your issue.
 

Last edited by JJinPA; 06-07-16 at 09:35 AM.
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Old 06-07-16, 07:58 AM
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By filter do you mean the filter that I change every month or so? If so, that is not dirty, I just changed it a few days ago.

Yes, it is extremely humid here right now.

Only a very small portion of the pvc pipe is visible (what you can see in the photo) so I really don't know if there is a p-trap or not.
 
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Old 06-07-16, 08:15 AM
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There is no trap visible in that picture and there should be one.

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Old 06-07-16, 09:20 AM
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I just asked about the filter because if its dirty, it would make no p-trap more of an issue. But higher humidity, if it is abnormally high, could also make no p-trap show itself. I have seen units running for years with no trap and no issues, but those systems also had incorrectly sized duct work as well.

It causes lower than normal air pressure in the cabinet, pre blower. This causes increased flow of air through condensate drain(higher pressure outside) A p-trap(once filled) cures this problem.
 
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Old 06-07-16, 10:00 AM
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So if we install a p-trap the leaking will stop? Even if the line is draining properly without it? I only ask because when I put my finger down in the line (where that inlet is for bleach) there is very little water in there, there's no clog or standing water there.
 
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Old 06-07-16, 10:13 AM
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If no p-trap is present, it should fix the problem. Unless you have bad/cracked drain pan, which I doubt.

Is it still leaking now? Once house dehumidifies, the leak may go away.

Do you know where drain goes to? Does it exit house or tie into a drain/etc?
 
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Old 06-07-16, 10:18 AM
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We looked at the drain pan, it seems fine. Not full and no cracks or anything. It is still leaking, but I haven't had the air on so I"m confused why it would still be producing water. Is that normal? And while it has been leaking for a few days now, the a/c was on all night last night (from 7pm until 6:30 am) before we noticed leaking again (we shop vac'd all the water up at 7 pm and more didn't appear until early a.m.)

The drain exits the house- there's a pipe that comes out of the ground by the side of the house.
 

Last edited by mickapoo; 06-07-16 at 10:36 AM.
  #11  
Old 06-07-16, 10:38 AM
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When you looked at coil, was unit off? Fan off? Once you shut system off, the negative pressure problem is gone and unit will drain. Take note of how much water comes out of drain(outside) when you shut unit off. Pan could be full, but drains once you shut system down to inspect(no more negative pressure).

If its off, it is not producing water. Either its residual water or another source.
 
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Old 06-07-16, 10:44 AM
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We first had the unit off when we looked at the coil. Then we turned it on.

So if we install a p-trap, the unit will stop leaking?

And I'm sorry for not understanding, so explain it to me in kindergarten terms, but if the drip pan is not full or cracked, and there is no water in the condensate line, where exactly is this water coming from that is leaking out the bottom? Meaning, not what is the cause per se, but where exactly is all this water dripping or running out of?
 
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Old 06-07-16, 11:26 AM
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Unless you have another water source nearby, it is just condensate water that has been absorbed by insulation/etc.

Just for giggles, put a level on the unit and the drain as well.

If you are running just the fan and you keep getting water, there is another source.

It could have been full/overflowing while running, but drained once you shut off it off.

Think of it this way. The trap creates a flowing wall of water that stops the flow of air through the piping. The pressure difference is not enough between outside and within the cabinet to lift the water backwards through the trap. But if no trap is present, it can be enough to impede the water flow enough where it can not keep up with what the pan is receiving from the coil.

Kind of like when tides get held up by hurricanes...Wind piles up the water and won't let it drain.

If no trap, start there, since it is needed. There could another reason, but fix the known problems first.

Would you say it is as humid as it has ever been? Abnormally humid? Usually no trap, if it doesn't leak right away, will do so on the more humid days or when filter gets clogged.

Is this the first time it has leaked?

Also, while rare, I have seen drains with no elbow on the end(with little pitch), go backwards up the outside of the pipe and leak back into house. Just add a 45(or 90) to end of the drain if it does not have one.
 

Last edited by JJinPA; 06-07-16 at 11:51 AM.
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Old 06-07-16, 12:04 PM
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I put a level on the unit and the drain, they are both nearly level (close, but not perfectly level).

I live in FL, and the humidity is high, but that's normal. We've had more humid, or at least as humid, days as these.

It has leaked maybe 4 or 5 times over the last 14 years (since I had the home built). Every time it was due to a clogged condensate line.
 
  #15  
Old 06-07-16, 12:21 PM
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The drain should have some pitch to it...If it indeed has no trap, lack of pitch will make the problem worse.

Near level is fine for unit if it is slightly pitched towards drain.

Did you have AC off for extended period before you started it up and had the leak? Was house itself extremely humid?
 
  #16  
Old 06-07-16, 12:28 PM
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No, it was only off for an hour or two, max, and the house itself is no more humid than normal. I just can't seem to observe any kind of pattern between having the a/c on and the leak. Sometimes the a/c is on and it leaks and sometimes it does not. Sometimes it is off and leaks.

Do you think I should turn off the a/c, check the drip pan and see if it's empty, then turn on the a/c and see if the drip pan fills up and does not drain? Or would that not help diagnose the problem?
 
  #17  
Old 06-07-16, 12:46 PM
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First thing would be to add a p-trap if none exists. Then run it and see what happens.

You could take off door and manually fill the pan and observe how it drains and if you get a leak...Is it metal or plastic(pan)?

Is there a bathroom above the unit? Only reason I ask is that the house I bought has shower directly above the unit and the drain was leaking. It happen to run down the return and made it look as if unit was leaking.
 
  #18  
Old 06-07-16, 12:56 PM
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Ok we will try adding a p-trap first. No, there is no bathroom above the a/c unit. Thanks for all of your help.
 
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