Thread: Condenser trap why?

What is the purpose of a trap on a condensate line from an AC unit?

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To keep the unit from sucking in/blowing out air through the condensate lines.

A few reasons:

Note the comment they included to describe that document:

"Our discussion will center on negative pressure systems, since trap failure in a positive pressure environment simply results in air being exhausted through the drain line."


Most all systems used around here are the positive pressure type.

I had a Trane gas pack on a previous house that had the negative pressure setup. I primed the trap at the start of the cooling season but most people do not.

I just finished an inspection of a crawl space and found: a Little Giant VCMA -15ult condensate pump attached to a high efficiency furnace. All good but, the poly pipe from the pump was inserted and glued into the side of an ABS drain pipe from the laundry room. The issue I have is that the poly pipe runs uphill without any way to prevent laundry water from running into the crawl space if the pump's back flow valve fails. The pipe was full of water so a pig tail or trap would not be useful. I could not get any info on the manufacturer's website on how they want their pump installed. Any thoughts from trap (or trapped) gurus?

The condensate tubing should run to a trapped location. Given the description you gave, I would run to the laundry as done but terminate with a washing machine box that has a receptor for condensate, i.e. Oatey Eliminator.

The homeowner isn't providing the required indirect connection and your concern is valid.

Even when the traps are installed I find many (as in today New Const.) that the cleanout/stand pipe is installed before the trap and not capped. Open stand pipes before the trap defeats the purpose of the trap.

Is there a code section that requires the condensate drain line, either primary or secondary to be p-trapped? If so, what is the code section?

thanks,

bm

Originally Posted by brianmiller

Is there a code section that requires the condensate drain line, either primary or secondary to be p-trapped? If so, what is the code section?

thanks,

bm

Hanging out at the pool (jury), so don't have the code no. but plumbing code requires each drain be trapped. And it is a drain line

Check for a recommendation/requirement in the manufacture's installation instructions (which code requiers be followed) - I have a collection of these to include in reports as required, and I keep adding to it from instructions left with un/mis-tapped lines. Sometimes it's a recommendation, sometimes it's a requirement, but it's almost always mentioned.

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As for "why", when I fnd un-trapped positively pressurized condensate drain line(s) I explain to clients that they are paying to air-condition the attic / sewer system / great outdoors / etc.... and if AC is running and the end of the line is accessible, I suggest they hold their hand in front of it.

I've search high-and-low but I can't find a code section (mechanical or in plumbing) that states a drain line or a condensate drain line,must be trapped; however, I may be needing new glasses and just can't find it....

I interpret the code to say basically, if you install a trap, do it in x-y-z way but I don't see where it says you must install a trap; but again, maybe I'm not finding the right section.

Originally Posted by brianmiller

I've search high-and-low but I can't find a code section (mechanical or in plumbing) that states a drain line or a condensate drain line,must be trapped; however, I may be needing new glasses and just can't find it....

Need to clean those old glasses ...

(bold and underlining are mine)
- M1401.1 Installation. Heating and cooling equipment and appliances shall be installed in accordance with the manufacturer’s installation instructions and the requirements of this code.

... and all the manufacturer's installation instructions I've read require traps - in both the primary and the secondary - condensate lines.