Reader Interactions


  1. I understand the need for a p-trap on the primary drain line, but why don’t you need one on the secondary line (to drain pan with level float switch)? Wouldn’t this drain blow air without a trap?

    • Hi Graham,
      That secondary drain line and pan are not under any kind of pressure, both fully open, so there’s nothing that would blow air into that drain line with or without the trap. On the contrary, one end of the primary condensate discharge line is fully enclosed by the coil compartment and pressurized at that end once the blower kicks in. Does that make sense…? Let me know.

  2. Questions,

    I am going to do a lot of the new attic location install of a heat pump and gas HVAC system. I have plenty of space and head room in the attic. Old HVAC closet too small for new high efficient units.

    I think I have a good handle on the extra drip pan, drains, and gas pipe. I know from talking to people and info on the web there are requirements for a walkway to the platform and requirements for the platform. I have been unable to find any specific general requirements as to height, width, and work area. Most of the pictures I have seen do not show a place to stand next to the unit.

    Do you have available a spec sheet that would address walkway and platform?

  3. I have two air conditions in the attic both are tied into one pipe that leads to the an upstairs bathroom drain, each air condition has a drip pan and each drip pan has it’s own pipe that leads to the outside of the house. My situation is that the drip pans are filling up and the water is dripping out of the pipes on the side of the house, and it seems that none of water is going through the one tied in pipe that lead to the upstarirs bathroom drain like should. I was told that the pipe was clogged and needed to be unclogged by blowing air through it. I had this done and it did not help the situation. Are my units installed correctly with this one pipe that lead to the drain or do I have another problem that requires more then just the pipes being unclogged with air being blown through them

    • Hi Derek,
      I don’t know if your condensate drain tubing is correctly installed, you didn’t explain how it is connected to that drain, its slope, etc. Just compare your installation with the description in my post. If it is a direct connection to the plumbing drain – it is wrong. Blowing air through the condensate drain pipe sometimes helps but I would suggest to open the coil compartment (turn the AC blower power OFF prior to cleaning procedure) and clean the drip pan underneath the coil (and the coil). If it doesn’t drain (assuming that you can see the discharge end / no condensate dripping out of it) it is still clogged / becomes clogged right after you blow some air through it, or it could be improperly pitched.

  4. Is the primary AC drip pan under the coil replaceable, OR you have to change the coil and the it’s pan at the same time? I am not talking about the secondary Pan.
    Thank you.

    • Hi Zaven,
      It depends on the design of the assembly. Older AC coil drip pans were metal and sometimes permanently attached / soldered to the coil itself. It might be possible to get the pan separated from the coil but I’m not sure if you can order a new one from the manufacturer. If it is a molded plastic drip pan, it’s usually secured to the coil brackets with screws, so it shouldn’t be a problem with taking it apart. Depending on the damage to the coil pan you may have another option; it’s a Drain Pan Repair Spray- , or this one –
      Friend of mine is a HVAC contractor and he did use the first one a few times – he says it worked fine.

  5. Are there any industry standards, or HVAC industry organizations, that call out the use of a drip pan in an attic installation? We do not have one installed in our attic. When I called the company who installed they said they never do that. Three other HVAC professionals have looked at it and asked why didn’t they install one. Just wondering what the industry standard is.

    • The post about the attic installed AC drip pan has been updated, let me know if you need more information

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