Condensate Drain P Trap for "Gas Pack" Package Unit

[lbperry]

My daughter just had a new Package Unit (Gas Pack) HVAC unit installed. I have a similar unit and it has a PVC P trap installed to drain the condensate.
When I looked over her unit it didn't have one installed; just the stub drain outside the units case that let the water puddle along the bottom of the case. At a minimum I plan to install a 3"-4" drain extension to get the water out into the lawn.
My real question is: Do I need to install a P trap also? I searched the forum and YouTube and got a wide range of answers from "You don't need one at all" to "You definitely need one". There were also a wide range of designs; All the way from the PVC "wave shaped" trap to some very elaborate designs.
From what I've seen, I doubt I'm going to get a definitive answer. But I'd like to hear some opinion on the need and design from some of you A/C gurus.
Thanks,

 

[shooon]

The main purpose of a P-trap is to prevent gasses from coming back up when tied into a drain system. Since you're draining the condensation on to a lawn and this isn't tied into a drain, IMO I don't see the benefit of having a P trap on this particular setup.


Edit: Just reread and noticed condensate not condensation. Best bet is get your hands on manufacturer documentation and see what they recommend for connections.

Second Edit:
Can you provide manufacturer make / model ?

 

[gungatim]

not familiar with your unit or a "gas pack" but around here, most hvac in homes just have pvc drain into a small plastic pump unit that pumps the condensate into the sewer lines. (think sump pump, only half the size of a shoe box). since my sewer line is above grade, the pump is required and a p-trap is installed where it enters the drain to prevent sewer gasses...my softener drains in the same trap which is open to the basement otherwise.

 

[Gila Monster]

I would put a running P trap on. You can get them pre-formed for like $2 at Home Depot.

Some units have negative pressure so its sucking outside, unfiltered air into your unit if it doesn't have that trap.

It also keeps things like bugs from crawling up inside your unit as there is a barrier.

 

[lbperry]

Thanks for the replies, guys. As you suggested, Shooon, I dug into the manufacturer documentation, and found the following statement: All units feature and internal trap of the condensate line eliminating the need for installing an on-sit external trap. I translate that to mean all I need to do is extend the existing stub outlet so the drainage will clear the case and frame and run away from the unit?
I was planning on installing a running P trap on it but looks like even that won't be needed.
Once again, thanks for the replies. They prompted me enough to go and RTDM (Read The Damn Manual). I should have done that to start with.

 

[handyman85]

I second what Gila Monster said; we have some commercial AC units at work that have enough negative pressure to pull air through the condensate drain hole preventing the water from draining - even to the point of overflowing the pan and getting insulation wet causing more issues.