Brand new TT has sewage odor

You said outside the trailer? Maybe someone did use facilities. Or, even just using the sink may create a smell in the tanks. That smell is gassing out the roof vents and when the wind is just right you are getting a whiff of it. If it's above freezing in your area I would add a few gallons of water to the tanks to dilute whatever is in there. That may help. There are also many different tank chemicals on the market and other methods to help control odors. Do a search on this site and you will find them.

COULD be the batteries off-gassing OR the delivery driver MAY have had an emergency on the way to the dealers facility :)

Was your trailer on display anywhere. I have helped my friend at RV shows and one thing we did was to tape the toilet seats shut so people, mainly their kids, would not use the facilities. A little bit in the tank can become mighty smelly. If it has been used make sure there is some water in the toilet bowel, that helps to seal off the valve and prevent odors from getting through.

I agree to check out for LP leak oder. It is about the same:E

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If getting smells within the RV/Chassis during towing, simply install the 360 Roof Top product. This product's design creates a negative air pressure above the vent pipe. Thus, "sucking" the bad air up and out the vent pipe. If wondering, normal vent caps don't create upward suction power. And sometimes, normal factory vents actually push air "down" the vent pipe while towing. Thus, pushing bad smells down (into) the tank and since pressurized air must come out, the bad air goes into the RV's chassis. Many times, I read the 360 siphon vent Product works great. Especially during towing (that makes wind - to create this upward suction). And, also works great when camping on windy days as well. For more details, surf: - click here -

If getting smells within the chassis on "no wind" situations, I read many time the Power Fan vent products works great. They can be either solar power, 12V power or even 110/120V power. I like the idea of solar power product (such as: - Click Here - ) but I read this product doesn't work well on NO sun days. Thus, I like the 12V or 110/120V power fan products (such as inline: - click here - ) much better. Especially with their manual off, low and high speed manual switches - regardless of wind/no wind and/or sun no sun days. Great inline power product but not too sure about removing bathroom wall panels - to install this inline vent pipe product.

Another great looking "roof top" product is the older style Little Stanker product. re: - Click Here - Think they stopped making this product 2 years ago. But, someone might have a similar product.

Hope this helps

Sometimes down drafts will force oder back into the trailer. I put an add on weather vain type vent top, it seems to help.

If it is pluged into 120, check the water level in the batteries. Had the same problem when my rig was new. Water was low and it cooked the batteries. Dealer had to replace them.

Not trying to be smart, but could it be LP?