I have a Rheem Criterion Gas Furnace. At the moment, my air conditioning system currently has low air pressure coming from the vents around the house. I double checked that the fan is working, replaced air filter, and checked outside condenser and made sure it is working. There is no water leaking, no ice formations around the copper pipe either. Not sure what the issue is.

Should any air be escaping from RED (with square-dash) PVC cover pictured below? Right now there is a lot of air coming out of it and not sure if this is normal.

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    are you certain that the air is escaping from the white pipe with the red plug?
    – jsotola
    Jul 9, 2020 at 3:33
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    The pipe on the left is a condensate drain. I think the red plug is a second outlet if needed. Any air coming out would be due to a leaky plug and the air pressure due to the blower.
    – DaveM
    Jul 9, 2020 at 4:06
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    That plug should not be leaking, I believe it is threaded. Even if that red plug is missing completely, it should not lower the air speed coming out of the vents by that much. Check the flex connection where the HVAC system connects to the ductwork (its about 2 inches high, usually black looking rubber) these rot over time and get holes in them to release a lot of air. Check any ductwork joints that you can see for leaks. If you find leaks, buy metal tape made for ductwork and seal everything.
    – Gunner
    Jul 9, 2020 at 10:06
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    How can there be "a lot" of air coming out around that plug? "A lot" to me means a substantial portion of what's being moved by the furnace. Even if the plug was completely gone, that little pipe couldn't allow "a lot" of air through it at fan pressure.
    – isherwood
    Jul 9, 2020 at 13:01
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    What type of ductwork? Is it located in a crawl space? If flex duct, I've seen situations where straps broke and the ducting fell down and partially kinked. Critters can also wreak havoc on flex ducts. If they get in the crawl those nice warm ducts are great to sleep on. That you have air coming out of that plug tells me you have back pressure. Just a thought. Other comments are good things to check as well. Jul 9, 2020 at 13:45

2 Answers 2


Just to answer your question, no, air should not be escaping from that red fitting. That is an extra drain pan fitting, maybe for a shutoff valve if the condensate backs up. Make sure the air is coming from that fitting and not from the cabinet around the PVC pipes. Try tightening the pipe and if that doesn't work, wrap some teflon tape around the fitting and screw it back in.

As mentioned in the comments, this will not have any effect on your air flow as the volume of air is so small. Check that the filter is the right size and that the blades of the blower fan are clean. this can really affect the efficiency for the blower.


Any air that is escaping from that white pipe with the red PVC cover is not affecting the air flow in your house. To find out if the air flow to your home is correct when the A/C is on, you could check the temperature drop across the A/C coil between the return duct and the supply duct just above the coil. To do this buy any temperature device that can be inserted into the duct work through any opening you can find. With the A/C running for at least 10 minutes record the temperature of the supply air and the return air. The difference should be between 15 and 20 degrees F. Too low is too much air flow and too much is not enough air flow. Be careful when inserting the probe that you do not harm the integrity of the coil. This measurement of temperature difference is just a "rule of thumb" but it is close enough. If the difference is not between the 2 readings then you may need to address fan speed, duct sizing, the amount of both supply and return registers and the condition of the A/C unit. my 2 cents

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