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I have a heat pump in the attic That drains to the ground outside two floors below. I naively added a hose fitting so I could redirect the water where I wanted it, slightly up hill. This created a trap in the line and my overflow pan filled. My HVAC soon shut off (2 days later) and I had to drain the overflow pan by hand. Removing the hose from the end of the drain and emptying the overflow pan allowed the System to start up again.

My question is: If I put a Y in the down pipe above my new intended outflow so that there is always a way for air to get out, will that cause any problems?

Diagram in text below:

Y    Site of possible Y
C  hose coupling     -------   End of Hose above coupling
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I'm thinking something else blocked your line. You would have had to run the end of the hose uphill a full two stories so that it was higher than the drain pan before it would cause a backup and overflow. – Dave Nay Jun 20 '12 at 2:25
@DaveNay Perhaps the trap on the bottom combined with the standard trap at the HVAC caused air to get locked in the line. As more water was forced into the bottom trap (in addition to temperature and outside air pressure changes), it increased air pressure in the line until gravity no longer forced water out of the top trap. That's just a theory, I could also see the top trap quickly blocking from algae growth promoted from the bottom trap being in contact with the ground. – BMitch Jun 20 '12 at 10:59
@BMitch. Perhaps....but Occam's Razor says that it is more likely to be caused by normal debris, bugs, accidentally jamming the garden hose end into the mud, or as you suggest algae growth. – Dave Nay Jun 20 '12 at 11:23
@BMitch The shut down occured 2 or 3 days after I added my hose trap. I have updated the description above stating so. – Aaron Jun 20 '12 at 12:42
@Aaron when you removed the hose, did it drain by itself or did you still have to drain the overflow pan by hand? If you still had to do it by hand, you have a blockage in the trap up top. – BMitch Jun 20 '12 at 13:37

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