Started getting a foul odour - smells like septic. Noticed it Friday night when we got to the trailer and thought it was a neighbor emptying tanks (we don't have sewer, just honey wagons).
Got worse over the weekend and last night it was really bad. This morning I dropped the coroplast down and looked around. There were no leaks anywhere and everything tight. Smelled good all day (or my nose got used to the smell). Started raining this afternoon and now we can smell the odour again.
Any suggestions?????

We had the same problem and it turned out to be our fresh water tank had never been emptied and given a thorough cleaning. (We purchased a used camper recently) We emptied the tanks and applied bleach and then another app of vinegar. Ran it through everything including hot water heater and washing machine. Now we smell like fresh clean water and roses in the camper!

Already cleaned fresh water tank in the spring when I brought it out of storage. That's not the problem. Any other suggestions??

You didn't mention f the odour is inside or outside of the Redwood. If it's inside, I've had a vent (designed to let air into the drain to improve flow) under the bathroom sink fail and let tank odours into the bathroom.

I also have had some external odours come out from the vents on the roof when dumping tanks, flushing the tanks reduces/eliminates the odours.

Thanks' for the answers.
The smell was only outside (except when you opened the door and windows).

Found the answer - it was my battery burning. Have a shorted cell and it is boiling the water out. Off to get new batteries.
Funny how I never even thought batteries but went straight to black tank problem.