Time out...
Another scary post from someone who appears to be extremely poorly informed.
I again send thanks to my original RV dealer who gave me a walk thorugh and explained A TON of important stuff.
If you don't know about your three tanks, I'm scared of the other stuff you may not know about of it...some of it has significant safety ramifications.
None of it's rocket science, but some of it might not be obvious either, and again, there's a good bit of stuff to learn.
I think you need to pause for a while, do a bunch of reading, maybe go see an RV dealer. There's also some books that do a nice job covering everything.