That is one reason I prefer my fresh water tank be empty or nearly empty when I travel. Our roads are so bad, I am surprised these trailers hole together as well as they do.
I fixed my squeaky floor by installing additional 2x3 supports with glue and a couple of screws from the top. Now it is quiet and feels like a concrete floor when I walk in that area. We also had a another noise in a different area where a bolt that holds the floor to the metal frame stripped. That noise was not a squeak, but we fixed it by lifting the carpet and just removing the bolt.