# so my question is this ....



## ironandfire (Oct 9, 2008)

How to determine the depth of the trap seal on a condensate line. My question may appear trivial but the job I'm on the original plumber put the vent between the coil and the trap. I'm fairly certain a 3/4" hole in the duct is not common practice. :icon_biggrin:


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## easttexasplumb (Oct 13, 2010)

We want pics


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## fightnews (Jun 3, 2012)

ironandfire said:


> How to determine the depth of the trap seal on a condensate line. My question may appear trivial but the job I'm on the original plumber put the vent between the coil and the trap. I'm fairly certain a 3/4" hole in the duct is not common practice. :icon_biggrin:


the depth of the trap should be 1" more than the max S.P. of the fan


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## ironandfire (Oct 9, 2008)

What's S. P. ?


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## Airgap (Dec 18, 2008)

Static Pressure


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## ironandfire (Oct 9, 2008)

Ah, and where would I find that info.


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## Airgap (Dec 18, 2008)

The trap seal has to be deep enough so the static pressure creatd by the fan won't blow the seal out. 

You have to know all the vitals on the equipment to figure the static press.


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## Airgap (Dec 18, 2008)

I would just call my HVAC buddy....Just get one of the preformed 3/4" cond. traps if it's residential.


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## ironandfire (Oct 9, 2008)

Their reasoning was the vent between coil and trap prevented that. NOT. Very good info, thanks.


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## ironandfire (Oct 9, 2008)

It's on commercial heat pumps.


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## Airgap (Dec 18, 2008)

ironandfire said:


> It's on commercial heat pumps.


Won't need to be real deep. use your gut. You'll know when you start it up and prime the trap if you've got air blowing through the drain....


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## BigDave (Mar 24, 2012)

http://t2.gstatic.com/images?q=tbn:ANd9GcR3HJ_kBxTH6o1p-UDzN48HinxbfMU-0BRg3_D1jC9BjeqnBX5j
This is accepted in my area, but most techs don't cap as long as top of vent is
above flood rim of pan under coil.


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## johnlewismcleod (Apr 6, 2012)

I'm a bit confused. The vent on a pan drain is supposed to be on the opposite side of the trap from the pan is what I've always been told...not between the trap and the pan.

The coil pan is atmospherically vented already, it's the drain line that needs to pull air to drain properly.

Maybe I'm missing the point of the question, though...like easttexas said already: a pic would be helpful.


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## ironandfire (Oct 9, 2008)

BigDave said:


> http://t2.gstatic.com/images?q=tbn:ANd9GcR3HJ_kBxTH6o1p-UDzN48HinxbfMU-0BRg3_D1jC9BjeqnBX5j
> This is accepted in my area, but most techs don't cap as long as top of vent is
> above flood rim of pan under coil.


No caps on these and not even a mention of them. I don't think I've ever seen the vent upstream of the trap.
I had mentioned this to the tinner and he said it was to keep the trap from blowing out. eek


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## ironandfire (Oct 9, 2008)

johnlewismcleod said:


> I'm a bit confused. The vent on a pan drain is supposed to be on the opposite side of the trap from the pan is what I've always been told...not between the trap and the pan.
> 
> The coil pan is atmospherically vented already, it's the drain line that needs to pull air to drain properly.
> 
> Maybe I'm missing the point of the question, though...like easttexas said already: a pic would be helpful.


No I think you understand it. I'll take pics tomorrow.


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## futz (Sep 17, 2009)

ironandfire said:


> Ah, and where would I find that info.


In my experience you would usually find the minimum trap seal spec in the manual for the machine you're draining.


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## RealLivePlumber (Jun 22, 2008)

I though as long as a water closet was not flushing past the 3/4" condensate line, it did not need to be revented. :laughing:




Seriously, you guys need to vent a condensate line?


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