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Author:
Pops Lopez (TX)
In TX is a p-trap required for my furnace / forced air unit. I was informed by the inspector that one is required. My home was built over 10 years ago? I spoke to another inspector and contractor who both stated that the trap is NOT required....
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Author:
ArthurPeabody (NM)
A p-trap keeps sewer gas from entering the house. If your furnace isn't connected to the sewer a p-trap can't serve that purpose. Also, if it's outside, it doesn't need one either. A p-trap doesn't keep sewer gas in the sewer but vents it above the roof. I'm not a plumber, so wait for one of those to answer.
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Author:
sum (FL)
It depends on the unit and locale.
I am in south Florida and all our residential HVAC systems require a trap, and there are codes governing this.
My understanding is from a DIY perspective, not an HVAC pro.
(1) First of all this is not a P-trap. A P-trap in plumbing has a U-bend AND a vent that goes to the roof or at least an AAV. A trap for the HVAC is usually not vented it merely provides a U for the water as there is no fixture draining by to siphon it. Many times there is a short riser that is capped to allow easy access to clean it.
(2) If there is an air handler inside, the condensate drain line exits the drain pan, and when the unit is running, there is negative pressure on the condensation, I have been told a trap is needed there to prevent the suction from causing the condensate draining easily. Although in my mind, I think if the condensate is emptying into a float switch activated condensate pump, that pump is really acting as a trap, but code still require it where we are.
(3) I have always moved the trap to the furthest point, in other words, outside the house where the condensate drain exits the house. This has the benefit of keeping critters like ants, lizards, roaches out of the line. To me the condensate drain trap is to keep critters out of the pipe.
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Author:
ArthurPeabody (NM)
You may get a better answer at heatinghelp.com. Your question is really a furnace question, not a plumbing question. My furnace is outside, doesn't need a trap.
Edited 1 times.
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Author:
ArthurPeabody (NM)
Condensate? Does a furnace need that? Or are you talking about combination furnace/AC?
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