First of all just so you know, there should NEVER be ANY smell coming from the tanks.
Did the people you bought this trailer from have it parked permanently in a park?
If so, some leave the black tank valve open all the time and there is not enough water to move the sewage out and it creates what we all call "a mountain of poop" in your black tank.
I hope for you that this is not the case.
For the quick fix until you can get out to a CG is fill up several gallon water jugs and schlep them out to your RV and pour them down into your black tank and add this:
Be sure to read the label and that it says
powerful odor control. There are 2 kinds on the shelf and look alike but the one marked natural doesn't do squat. Find at any Walmart.
I'd put 2 bottles of it in. This stuff actually 'Break down Waste' others do not. I use this stuff regularly.
For the gray tank put a gallon of water and any quart size liquid lemon cleaner from the grocery store.
Pour water down all sinks and the shower AND.....put water in the bowl of toilet when done. P-traps Need to be filled and toilet with water to create a seal just like in you home.
THAT should get you to the CG without you and the DW gagging!
Good luck. Once you get over this oops you should be fine.
Don't forget the
