I am modifying the drain pipe that drains my inside AC unit. When I purchased the home, there was an electric drain pump tied to the unit. Upon investigating why the unit needed one I found a pipe in the wall that used to drain the old AC system. The problem is the drain was too high in the wall to be used on the new AC when the previous owner replaced it.

So I opened up the wall and rerouted the pipe so it was at the same level. My problem is that the end of the drain is just barely low enough to create the minimum slope needed for water to drain correctly ( 1/4 inch drop per 1ft).

To make this work with a condensation drain trap, I was wondering if I could used the secondary drain coming off the unit as the main drain. This is because the secondary drain is about an inch higher then the main. If cant do this then I wont be able to use a condensation trap.

How important is the condensation drain and can I use the secondary drain rather then the main. Thanks guys!

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  • 1/8" per foot is fine. What's with the moldy plywood? I'm wondering how this unit can even work if it has a Safe-T-switch and the drain not where it should be (where red cap is), the top drain port is for horizontal installations. Where's that elbow sticking out of the plywood go? – Mazura Jul 25 '15 at 19:58
  • The point was to show what I was explaining in the question. The pvc coming out of the plywood was how the system used to drain. Into an electric pump inside the return. – Nate S. Jul 26 '15 at 2:11

The trap in the condensate drain, prevents the unit from sucking air from; or blowing air into, the drain line. Without the trap, the condensate may not drain until the blower turns off. This could lead to the pan overflowing. So you can't remove that.

The secondary drain is typically for situations when the main drain is blocked, or otherwise insufficient. In some units, condensate only reaches the secondary drain when the pan overflows. If this is the case, using the secondary drain as a main, would allow water to sit stagnant in the pan. So you probably won't be able to use it as the main drain, but it may vary depending on the unit.

  • Originally the secondary trap had a red plug and wasn't being used anyway. Without the using the secondary drain, I wont be able to have the trap. Which is more important? – Nate S. Jul 25 '15 at 18:14
  • Without knowing the make and model of the unit; or seeing the inside of the pan, I can't say for sure if using the secondary drain is advisable. – Tester101 Jul 25 '15 at 18:49
  • @NateS. I've added more details to my answer. In the end it's your home, you can do what you want. – Tester101 Jul 25 '15 at 18:54

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