P-trap in drain line?
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  1. #1
    Join Date
    Dec 2006
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    P-trap in drain line?

    Should the drip line from the inside unit of a heat pump have a P-trap when the line is routed directly outside?

    A recent home addition included a heat pump with the inside unit located in the attic. The drain line has a P-trap right at the inside unit. Than the line runs about 18' to an exterior wall and 17' down the wall to a point about 1' above grade.

    My concern is that, over time, sediment will not be flushed in this low volume application and cause leakage problems in the long term.

    Do you guys use P-traps in similar applications? If not, would you remove an existing one?

  2. #2
    Join Date
    Dec 2002
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    Believe it or not the chances are greater for line stoppage without a trap, but you have to have a good understanding of how the trap works to understand me on this, plus a trap will keep odors out of your home that "can" be picked up through the drain line.
    Odors are not as common when the line is ran outside but they can develop after a long period of time from just the build up in the line itself, I hope this gives you a little prospective on your question.
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  3. #3
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    Apr 2007
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    I have a p-trap on almost every unit in my complex that I have come across. 227 units the few that didn't have them that I have seen (which I fixed) did have more buildup in them. One actually was clogged and was using the secondary drain for condensate, not to mention you can feel a slight bit of air coming out of the pipe without the trap which is lost to the drain when it could be helping to cool. (know it's minimal but every bit helps)

  4. #4
    Join Date
    Dec 2006
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    The reason I am concerned about the P-trap in the attic is because of problems with my other heat pump where the inside unit is in the basement. Years ago, I suddenly had water all over my unfiniished basement floor.

    The problem was the P-trap was blocked with sediment. I "fixed" the problem by replacing the P-trap with a system where two ends are not solvent welded. Every year or two, I pull the P-trap out and flush it out with a hose.

    Granted my old heat pump is quite aged and discharging sediment much more than my new unit; but, I hope to not replace the new unit for a long time. Since I already have a history of problems, I am wary of a P-trap above my finished living areas.

    Does the location over finished living areas alter suggestions?

  5. #5
    Join Date
    Apr 2007
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    By a el cheapo brush something like a coil brush from home depot (it looks like a bigger pipe cleaner and is bendable) When you clean out your p-trap. But honestly you should have your system PM every year and that should be included along with coil cleans and filter changes. Just my opinion. You can by pan tabs from the store that cut down on sediment buildup.


    Also older drain pans were made of metal and the obvious ill effects of water and metal made that much worse...Newer ones are made of plastic. Well at least from what little experience I have.

  6. #6
    Join Date
    Mar 2007
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    Myrtle Beach, SC
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    Yes leave the trap in. There should be an emergency drain pan under the indoor unit in the attic. You should have the system checked every year and they should clean out the drain as well as add drain treatment.

    Tooting my own horn, but check these out.....

    Solve Condensate Drain Problems
    http://www.contractingbusiness.com/2...le/False/5349/

    Heat Pump Tune-ups
    http://www.contractingbusiness.com/2...e/False/31870/
    Remember, Air Conditioning begins with AIR.

  7. #7
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    Feb 2007
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    Southern California, LA Metro
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    Fan coil units are typically used for heat pump systems. Their coils and drain pans have negative air pressure during operation. Without a properly designed Ptrap the water cannot drain properly, sometimes not at all until the fan stops.
    A secondary drain pan should always be installed under the unit when in the attic or anyplace above conditioned space.
    Larger Duct, Larger Duct, More Air, More Air
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  8. #8
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    Nov 2006
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    if the attic unit is an air handler then you need a trap in the condensate line because the evaporator is on the negative side of the blower.find a reputable contractor and have seasonal maintainance done (service contract) and you should not have any problems with drains,and it will keep your equipment in top condition.

  9. #9
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    Jan 2002
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    Ft.Worth,Tx
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    Thumbs up

    If the coil is in the return with airflow being pulled ,a trap is needed, if coil is in the supply and airflow is being blown through, then no trap is needed. But, some put traps on all coils ; installation verys from company to company.

    As to dump drains on outside be careful , bugs like to crawl into drains and make a home , stopping up drain lines.
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  10. #10
    Join Date
    May 2004
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    Frederick, MD
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    905

    added protection

    Don't know if this was mentioned, but for added protection, buy the trap that has the switch installed to break the circuit of the unit in case the trap clogs. Also, make sure there is an auxiliary drain pan under the unit and it is piped separately to the outside. No trap is needed in that line (unless local codes require it) and some folks put a float switch in the pan incase that backs up too. Kinda like wearing a belt and suspenders, if you know what I mean.

  11. #11
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    Aug 2004
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    To elaborate on oldertech's reply, without the trap, the system will not drain until the blower turns off. Not only will this allow a greater amount of "sediment" to remain in the pan, it will also create greater summer time humidity levels.
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  12. #12
    Join Date
    Feb 2007
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    Southern California, LA Metro
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    Quote Originally Posted by lra View Post
    To elaborate on oldertech's reply, without the trap, the system will not drain until the blower turns off. Not only will this allow a greater amount of "sediment" to remain in the pan, it will also create greater summer time humidity levels.
    Thanks Ira

    To further elaborate, no drainage also equal leaks or secondary drainage. However if installers didn't trap primary the secondary probably didn't get trapped either and won't drain.
    Larger Duct, Larger Duct, More Air, More Air
    READ THE MANUAL
    What if I train them and they leave?
    What if you Don't train them and they Stay!
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  13. #13
    frank29

    Do you guys use P-traps in similar applications? If not, would you remove an existing one?
    Is there a manufacturer out there that does not indicate that a trap must be used to terminate condensate?
    Always use a trap unless otherwise indicated in installation specs.

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