Condensate line design

[Tom Rees]

OK, So I finally see a condensate line with a trap installed. In my area 98% do not have a trap installed in line. However it appears to me that the cleanout is left open which would nullify the purpose of the trap, or this was supposed to be the vent which is installed on wrong side of trap. Am I seeing this right? I found the two condensate articles on this site which are very helpful.

[Bob Harper]

Is that lower gas cock for the WH?

I always install a cleanout tee in front of the coil because that's where most of the goo and crud will block drainage. If it is draining properly, the air in the coil will provide the back-venting. The arrangement you show is typically plugged with a short length that fits down into the riser with a cap cemented on but the plug removeable.

Traps required where it pulls through: good idea and maybe energy code issue on blow-thoughs.

[Tom Rees]

I believe that is for the water heater Bob.

[Bob Harper]

Thought so. It really should be off a separate feed so that if the furnace is shutdown it does not kill the WH. That's why I asked.

[Jerry Peck]

In my area 98% do not have a trap installed in line.

That is not good, a trap is needed for several reasons.


However it appears to me that the cleanout is left open which would nullify the purpose of the trap, or this was supposed to be the vent which is installed on wrong side of trap. Am I seeing this right?

With the top of that tee left open, yes, that creates a vent on the wrong side of the tee. That top should be plugged, preferably a glued in plug.

[Jim Luttrall]

As your documentation shows, the trap is required by the manufacturer on either type of system (blow or draw through) the vent goes on the downstream side of the trap, just like any other plumbing vent. I call for a dry fit cap on the upstream vent so it can be used for a clean-out and then add a downstream vent.

[Tom Rees]

I like this design: http://www.alpha-eproducts.com/files/2193829/uploaded/EZ%20Trap5.jpg

Thanks Bob, Good eye on the gas line.

[Bob Spermo]

Most (if not all) manufacturers require a trap on the condensate line regardless of the location of the coil in the air handler.

[Jim Luttrall]

I like this design: http://www.alpha-eproducts.com/files/2193829/uploaded/EZ%20Trap5.jpg

Thanks Bob, Good eye on the gas line.
Good design but the cap on the vent should be removed. It the caps are left attached, someone will likely reinstall it like the one in the picture.
The vent opening should be elevated above the "flood rim" of the pan.

[Jerry Peck]

I like this design: http://www.alpha-eproducts.com/files/2193829/uploaded/EZ%20Trap5.jpg

One problem with many of those cut-off switches like that one installed in the secondary condensate drain opening (which is where they should be installed) is that many of them as designed such that the water level in the switch housing (a standard 3/4" tee) often has to rise so high to shut the unit down that the water overflows the edge of the condensate pan built into the equipment - not good.

That design is not as good as it looks to be as there is insufficient height for the likely static pressure inside the AHU (refer to those documents which were posted and you will see what I am referring to).