Air Leakage from Sump

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by CarlH, Jun 14, 2011.

  1. CarlH

    CarlH New Member

    Messages:
    175
    Location:
    Northern VA
    I get air coming in from my sump pit whenever something in the house forces air outside such as a bathroom fan or the clothes dryer. My basement has no exits and therefore no exterior drains. The tiles should be completely below grade and covered with soil. My best guess for the source of incoming air is the gap between the garage floor and the foundation. I think there is a few feet deep of gravel under the garage floor and that air can get through the gap and then the gravel to the tiles and then from the tiles to the sump pit. I did caulk the gap between the garage floor where it meets the foundation, but that did not solve the problem. That leaves a few more possible places for air to come in such as the rest of the gap between the garage floor and the garage foundation, the gap between the driveway and the garage floor and a small area where the driveway meets up with the foundation.

    It would be really great if I could pinpoint the source of the air leakage. Sealing the sump is not really an option at this point since I have a drain pan for a 2nd floor washing machine that runs to the sump. Sealing the sump with washing machine pan line in place would send the musty air up to the second floor.

    Does anybody have any thoughts or suggestions on how to pinpoint the source of the leak?
  2. DonL

    DonL Jack of all trades

    Messages:
    3,819
    Location:
    Houston, TX
    Smoke test...
  3. CarlH

    CarlH New Member

    Messages:
    175
    Location:
    Northern VA
    I was sort of doing that, but with wrong approach. I was using the negative pressure from the house with all of the exhaust/bath fans on and searching for the source of the incoming air with a incense stick. I did find an area where air was coming in and used caulk to seal it, but that was leak that was not going to the sump or not the only one.

    I like the idea of doing the smoke test to show me the leak instead rather than me searching for the leak. I happen to have a spare bath fan that I can use to deliver the smoke. Now all I have to do is fab up a cover for the sump and find some smoke bombs. Being the time of year it is, I can get some from a local fireworks stand, but I'm not sure of their safety, sulfur smell, and quantity of smoke. I think I should order the proper kind...
  4. cwhyu2

    cwhyu2 Consultant

    Messages:
    1,331
    Location:
    Cincinnati OH
  5. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,309
    Location:
    Cave Creek, Arizona
    I hope you do not have any gas burning appliances, because if the house is that tight, you have a major issue with combustion air.
  6. CarlH

    CarlH New Member

    Messages:
    175
    Location:
    Northern VA
    My house is not that tight. It seems that drain tiles flow that much air. I have checked the draft at the water heater after plugging other leaks in the past and we do have two carbon monoxide detectors in the house.

    I did connect a bath fan to the sump. It is delivering air with some resistance, but not too much. It is probably delivering at least 45 CFM of air. We get very little air through the sump in comparison to the amount being vented from the house. It makes me wonder where this is leaking with me being able to put some much air down there.
  7. DonL

    DonL Jack of all trades

    Messages:
    3,819
    Location:
    Houston, TX
    Are you saying that you pressurize the basement with a 45 CFM fan ?

    Or are you sucking the air out ?


    DonL
  8. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,841
    Location:
    NW Ontario, Canada
    My house has a HRV that runs constantly on low speed, kicked up to high speed by crank timers. I have a small line to the HRV drawing air from the sump pit.
  9. CarlH

    CarlH New Member

    Messages:
    175
    Location:
    Northern VA
    No, not the basement. That would be rather difficult. The discharge from the bath fan is running to the sump pit. Basically it is set up in a manner you would need to do for a smoke test. I'm just surprised that the fan did not meet more resistance. Smoke pellets on order. I should probably notify one of my busy body neighbors before running the test so that I don't end up having a visit from the fire dept.
  10. bulldog plumbing

    bulldog plumbing New Member

    Messages:
    12
    Location:
    batavia il
    all carbon monoxide detectors fail after a period of time, i would test them.
  11. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,309
    Location:
    Cave Creek, Arizona
    quote; It seems that drain tiles flow that much air.

    That borders on the IMPOSSIBLE, unless the earth around the drain tiles is so porous that air can be sucked through the ground and into the drain tiles.
  12. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,841
    Location:
    NW Ontario, Canada
    Maybe his drain tile goes up into window wells.
  13. CarlH

    CarlH New Member

    Messages:
    175
    Location:
    Northern VA
    Good call, but I my basement windows are 12" high and above grade, so no window wells.

    The earth around the drain tiles is mostly red clay and not porous. It is certainly possible that all of the air I was pumping into the sump pit may have not been flowing outside of the envelope. Some of it may have been flowing through the gap between the basement floor and the foundation. When I depressurize the house by running all of the exhaust fans and clothes dryer which would be in the ballpark of 500 CFM I get maybe 5 or 10 CFM from the sump pit and that air has got to coming from somewhere outside the envelope.

    Maybe a little more history and details may help. From what I was told, when they were digging the foundation they hit rock and had to do some blasting, removed too much, and then had to fill with gravel before putting in the foundation. I did not see the situation and cannot verify that as fact. About 10 years ago the water supply between the meter(located near the road) and the house ruptured. The original supply entered the house from below the foundation and since it was so deep we elected to abandon the original line and install a new one. I presume that since I could hear the leak inside the house, that the rupture was closer to the house than the meter. The line was leaking for several days and I have no idea where the water was going. There was no water flowing from the tiles to the sump pit. This make me wonder if a possible air source for the drain tiles is that abandoned line. If the rupture is at or near the drain tiles and I assume the other end near the meter has been left open, that some of the air could be coming in through that line. Something else that has been in the back of my mind is the possibility that the sewer line from the house could have been damaged in the same manner that caused the water supply to rupture. I hope that is not the case and if it were I would assume that the air coming form the sump would smell more than just musty.

    I did manage to caulk the perimeter of the garage floor and that did not seem to help. At least that has been ruled out as a possible source. I think I will do the same for the basement floor. That way when I do a smoke test, I won't get smoke flowing coming back into the house in the event there is some flow between this gap and the sump.
  14. CarlH

    CarlH New Member

    Messages:
    175
    Location:
    Northern VA
    My smoke bombs came in today and I just had to try them out. I used three bombs at separate times and have no idea where the smoke went. I went with the small size that has a 45sec burn time for 150 cu. ft. of smoke and they must be too small for this task with the smoke getting to diluted by the time it exits. I guess the next thing I will try is to triple up the ones that I have.

    Another option is to seal up the sump and provide it with an external vent. Does anybody know if there is some sort of check valve that would allow water to flow down from the washing machine pan but not allow air to flow up. I have not seen the guts of a sump pump check valve, but this would not work in this situation, right?
  15. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,309
    Location:
    Cave Creek, Arizona
    Do you have ANY gas appliances or fireplaces in this house?
  16. CarlH

    CarlH New Member

    Messages:
    175
    Location:
    Northern VA
    Yes, a water heater and a furnace.
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