"Trap" in A/C Drain

My attic installed A/C has one drain from the pan under it, which is not the issue here. The A/C itsself has a "J" shaped trap of some sort, contructed of cast iron pipe about 1' out from the A/C. All other drain piping is flexible black plastic. Intake to trap is higher than output. About 6" beyond that is a capped plastic fitting which I have always used to induce bleach into pipe to preclude downstream fouling by build up. I can see that the trap would preclude backflow, but over time, it has filled with rust, becoming part of the problem vice part of the solution. Question: Is this "trap" called something so that I can go to an A/C parts dealer and get one? My guess is that the original trap was fabricated on site by the installer. Why he used cast iron pipe is beyond me. So, could I just build one up with "L's", etc. for an in-ground lawn sprinkling sytem, or even PVC---or is there some stupid code that dictates it be as it is?
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No reason not to use plastic.Just be sure you build the new trap exactly the same size and shape as the old one.Changing size and shape in anyway will cause the condensate not to drain properly or not at all.

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Many coil installations call for a R-trap to be installed close to the coil yours may call for a J bend. A J-bend is common for heat pump systems where the coil is on the return side of the air flow, R-trap are more common for A/C systems. You could replace the entire drain line and j-bend in pvc.

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The trap is only needed if the drain goes into a sewer -- where sewer gasses might come back. If it drains out onto a sidewalk, or into a sump pump crock, there is no advantage to a trap.
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???
Sometime when you're helping your 'Boss' you might take a moment to read the installation instructions regarding the installation of a trap at the outlet of the condensate drain most especially when the application is running the evaporator in the return side. Please do so before handing out such advice as you gave above since you most likely won't pay to replace the OP's ceiling.
- Robert
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A p-trap is to break the suction and allow the drain to function. Normally the drain is on the suction side of the blower evap coil. I don't think they make the drains on the blow side of the evap coil but I could be wrong about that.
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'The trap is only needed if the drain goes into a sewer -- where sewer gasses might come back. If it drains out onto a sidewalk, or into a sump pump crock, there is no advantage to a trap.
--
Christopher A. Youn'

ME: Not totally correct. You need a trap if the cooling coil is on the
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Chris, please learn about HVAC before you give advice on the subject.
For you have NOT a clue for the real purpose of a trap.
~kjpro~
BTW, Dave is a complete moron, just like stormy.
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OK I'll throw in my two cents.
Like referenced above, the condensate drain trap is needed where the cooling coil is on the suction side (negative pressure) of the fan. The trap provides a pressure seal between the inside of your systems and the outside. Without the p-trap, air would be constantly sucked into the coil plenum through the untrapped condensate drain and it will be very difficult for the condensate water to drain out of your unit. If you had a clear condensate drain line, when you unit is operating, you would see a slight difference in the water level at each leg of the condensate drain trap. That's because the air within you cooling coil plenem is trying to suck the water into the plenum. Measure that distance and you have the pressure difference between the outside and your coil plenum.
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True. But be sure to put a sign at the end of the pipe "No Bugs Allowed". That will work.
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Hi Stormin, hope you are having a nice day
On 11-Jun-04 At About 03:34:18, Stormin Mormon wrote to Stormin Mormon Subject: Re: "Trap" in A/C Drain
SM> The trap is only needed if the drain goes into a sewer --where sewer SM> gasses might come back. If it drains out onto a sidewalk, or into SM> a sump pump crock, there is no advantage to a trap.
This is total BULL!! I want you to tell me what the trap is really for ( If you can )
-=> HvacTech2 <=-
.. "Aw mom, you act like I'm not even wearing a bunji cord!"
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About how/whether to replace the cast-iron pipe trap in my A/C drain line as the cast iron was rusting closed. Many thanks to y'all for the inputs, though you lose me a bit when you start talking about pressure differentials. I went to H.D. and their "expert" tried to sell me what looked like a piece of PVC with a lazy sag in the middle (about 1" lower that both ends---which were at the same height). SInce one of you wanted that what I put in should look equal to what I took out, I made one out of yard sprinkler system black plastic pipe. with attendent fittings, els, etc. Works fine; water is coming out the discarge end, the pan and the pan discarge are dry. Again, thanks
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wrote:

That was a P trap, and it would have worked fine..so would a S trap, had they had that.

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wrote:

That would have been a (R) running trap.............
A *P* trap doesn't have the ends at the same height. :-)
~kjpro~
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wrote:

You havent seen the P types they sell at Homey Depoot then? :)

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wrote:

NOPE, there NOT on my list for distributors!! :-)
And they won't ever bee!!
~kjpro~
BTW, what the hell you doing in one?? LOL
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