I'm trying to install a whole-home humidifier. I'm wondering whether I can use these copper pipes as supply lines for the humidifier. Any guesses as to what pipes A, B, and (just out of curiosity) C do? I believe they're connected to a condensate drain, but am wondering where they come from.

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  • 1
    what is on the yellow tag? ... why would there be water connected to a furnace? – jsotola Mar 4 '18 at 23:43
  • A & B look like copper. Which is not normally used for gas - but the cutoff valves and everything below looks like gas. Is the yellow tag a "didn't pass inspection" notice? – manassehkatz-Reinstate Monica Mar 5 '18 at 0:06

A and B look to be a gas line of one nature or another, whether it be natural gas or liquid propane (LP), C is the conduit that feeds electric to the unit.

Either A or B supplies the unit, and the other branches off to supply fuel for another appliance that requires gas.

  • I was wondering what that yellow tag attached to “B” says. – herb guy Mar 4 '18 at 23:43
  • Yellow is the color code for gas, so it might say do not use this as a water supply, it will blow your crap up. – Jack Mar 4 '18 at 23:44
  • Why would gas lines be connected to a drain? This might be a good time to mention that I don't know much about HVAC. – RobertAKARobin Mar 4 '18 at 23:55
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    The drain is for condensate build up in the gas line, that is if you are referring to the extension below the part going to the furnace with the cap on the end. – Jack Mar 5 '18 at 0:01
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    Your gas line, the copper and the black pipe, are NOT connected to a drain. The small piece of black pipe on the bottom is a drip leg to catch any solid particles in the gas so they do not make it into the burners. You should check with you local municipality to see if copper is allowed by code. You also need to research how a humidifier is installed into a forced air heating system. – Alaska Man Mar 5 '18 at 0:39

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