air handler condensation drain trap

[Hardly Workin]

I have a brand new airhandler, and have the install nearly completed. I note the paperwork with the unit says, that i should have a trap in the condensation drain. The pipe size is 3/4"..
a check at local home building supplys does not turn up any traps that small.. where would i get one of these, and if i don't have it will it mess me up in the future?
any info you have on this will be read and appreciated.. thanks
HW

[UO_Woody]

HW,

Though I am by no means giving advice here, I have seen 1000's of all sizes of these units. Being a commercial flat roofer, I deal with these things daily. I can tell you that if there is no trap, it can leak inside the building.

This is a discription of a typical trap I've had to deal with:

Horizontal pvc to a elbow going down, to a elbow going horizontal, into a elbow going vertical, to a elbow going horizontal. As long as the final elbow is just below the unit's drain, you have created a trap.

From experience, removing the trap, the unit can freely suck air through the drain, letting the water build up and spill over inside the unit. Similar to draining your air compressor. Do it with full tank of air, you'll get no water. With very little air, all water is released. Water will only drain off when the unit is not running without a trap.

Hope this was what you were looking for.

[geoken]

Originally posted by UO_Woody:
HW,

Though I am by no means giving advice here, I have seen 1000's of all sizes of these units. Being a commercial flat roofer, I deal with these things daily. I can tell you that if there is no trap, it can leak inside the building.

This is a discription of a typical trap I've had to deal with:

Horizontal pvc to a elbow going down, to a elbow going horizontal, into a elbow going vertical, to a elbow going horizontal. As long as the final elbow is just below the unit's drain, you have created a trap.

From experience, removing the trap, the unit can freely suck air through the drain, letting the water build up and spill over inside the unit. Similar to draining your air compressor. Do it with full tank of air, you'll get no water. With very little air, all water is released. Water will only drain off when the unit is not running without a trap.

Hope this was what you were looking for.

[geoken]

Go to a HVAC supply house, most have preformed PVC or ABS traps in stock or just make your own.

[Hardly Workin]

Thanks for the help.. i have tried in the past to purchase from the HVAC houses here in florida, but they only sell to licensed AC outfits. I got a cousin to purchase the new airhandler for me, he works for a big mechanical contracter. I can find all kinds of inch and a quarter and up traps..but have not found a smaller one.
i guess i will have to get a few elbows and make one up as you say.. i was hopin there was a place i could purchase one online, but could not find that either.
thanks for the help. gotta get it finished up now. summer is here.

Hardly Workin

[hvacrus]

Traps are absolutely mandatory installs on any application where the blower PULLS the air over the coil. Without it, the negative pressure created by the blower will pull water back through the condensate drain, into the air handler. If the A/C coil is mounted on a furnace, they are NOT necessary because the blower is PUSHING the air over the coil, and therefore the condensation through the tubing. There is no danger of backfilling.

You might want to add a TEE in place of one of the ELLs in the bottom if you make your own trap.

Let the bull (the side opening) of the TEE look up and connect one end of the run (straight through the TEE) as part of the trap. On the other end of the run glue in an FM pipe adapter and screw in a PCV pipe plug (don't forget some pipe dope or Teflon tape). The plug can be used as a cleanout. Remember your trap built out of fittings will be glued together and can't be disassembled for maintenance/cleaning.

Either that or put a couple unions in so you can remove the trap to clean it out at least yearly.
if you go with unions place one in the drop down from the drain pan before the first 90 and the second on the horziontal run towards the drain after the last 90 in the trap. PVC traps are cheap and will make cleaning the trap so much easier you won't regret putting them in.

I have found pre-fab 3/4" PVC condensate traps at my local home depot up on a high shelf. If you decide to fabricate your own be sure not to make it too large or on a hot humid day condensate will form on the exterior of the trap.

I have found pre-fab 3/4" PVC condensate traps at my local home depot up on a high shelf. If you decide to fabricate your own be sure not to make it too large or on a hot humid day condensate will form on the exterior of the trap. The addition of a tee at the air handler side of the trap is a great idea for cleaning.

[photoman250]

I'm an install mechanic for an HVAC contractor, you can make your own "P" trap using (3) 3/4 inch pvc 45's. works very well too. "P" traps are a must on airhandlers the pull air across the coil, or when you have a coil below the blower.