Stack Exhaust Fan

[adamells]

Hi, I've found several questions answered on these forums over the last few months but time to ask a quick question.

I work in a new 10,000 sq ft. building that's basically a warehouse with a raised floor (for data center/call center use). For now I'm the only one in the building. Not long after I shut down the A/C system for the winter I started to notice a funky smell - at first I was afraid something died under the floor and I'd never find it, but eventually I found the cause: The building is extremely airtight (and no openable windows) and if the building develops any sort of negative pressure, as small as the bathroom fan running in the opposite end of the building, air comes in from the sanitary vent stack through a floor drain under my office.

I'm nearly certain there's no trap in that drain, and I've poured a few gallons of water down in case it just evaporated - no such luck. Since the building has already been signed-off on, the contractor doesn't seem interested in replacing it, so we will have to have it jackhammered and replaced at some point I suppose, but we'll need a little more cash flow before I can do that. In the meantime, is there a small fan assembly I can slip onto the vent on the roof (which is easily accessible) to ensure outward flow? I'm worried a check valve would simply stay shut all the time (if the building is "usually" negative) and defeat the purpose of having a vent.

Any ideas or suggestions?

[markts30]

If it is just the one floor drain that is emiting the odor, you could plug it temporarily till you get it fixed with a "dollar plug"
http://www.lspproducts.com/SpecSheets/SpecialtyProducts/TestingDevices/ExpansionDollarPlug.pdf

[hj]

Pour antifreeze into the drain. It will not evaporate. RV anitfreeze would be better, but since the amount you would use is insignificant, a couple of cups of automotive antifreeze would also work. Another source of the smell might be if the air conditioner condensate drains into the sanitary system by means of a connection other than through a sink or other water using item with its own trap.

[Gencon]

Have a primer installed on one of the bathroom fixtures.

[SteveW]

I'm nearly certain there's no trap in that drain,

Is this possible?

[adamells]

Thanks for the suggestions so far... no such luck though:

- The drain must remain open, the hose from the air conditioner and steam humidifier system (which auto-flushes several times a day) drain into it, and those run year-round for the computer room.

- I'm certain the trap hasn't simply dried, which was a suggestion I did find on these boards and discovered in the restroom drains, so when *they* started to smell it was my first thought and easily fixed the problem.

There's not even a strainer on this drain, it's a 3" PVC pipe in the floor that appears to go straight down two feet or so and then heads straight for the main stack. I've poured a few gallons of water down this which disappears immediately... I can see the bottom and it's just an elbow.

I mean, I guess the solution is pretty clear, the drain's going to have to be torn up and re-installed with a trap. Fortunately there does seem to be plenty of depth to work with, and since there's a false floor above the concrete it hardly even has to look good. I just can't imagine this is "up to code" and for a $1.2 million building that's only 10,000 sq feet you'd think most things would have been done correctly. That's what they get for signing off on the building 9 months ago without a project manager or competent inspection. :-/ Whole thing feels like there's a week and a half of construction left.

(edit)

I guess I was repeating myself a bit... back to my original question, do they make any sort of fan I can put on the vent stack that ensures airflow out of the system? Since the drain IS open to the inside air, it wouldn't even create a vacuum in this case (or trivial one anyway). I just need to stop air flowing INTO the building through the vent. (And I don't want to use a check valve, even if it's allowed, because if the pressure was higher outside, then *concentrated* odor would flow into my room instead of a mix of outside air!)

My best guess is somebody misunderstood the floor plan and thought this was going to be a sink or another vent before the foundation was poured.

[jadnashua]

If all drains have vents and traps, there is no place for sewer gasses to come into the building except from maybe a roof air intake. If those are near the vents, someone did a really poor design. A forced exhaust on the venting system would have no effect on this. It is not uncommon to have the building under positive pressure to prevent stuff from entering. Adding an exhaust fan to the venting system is probably a waste of time. It should NOT be directly open to the inside, there should be a trap between each vent and its fixture.

[adamells]

There are no intakes on the roof, just two sewer vents, but this drain has no trap and the building often has negative pressure.

Apparently the only solution (besides being the only correct one) is to redo the drain from scratch and install a trap.

I'll see how far a sledgehammer gets me. Beyond that it might not be that difficult. Just a lot of digging... but there's plenty of depth before the elbow, so I only have to go deep enough for the trap to fit and I'm done.