Do you by chance have an outdoor shower?
The reason I ask is, I bought our 222 Octane SL in November and it was winterized by the previous owner. In the spring, I did the unwinterizing and off we went camping. But wow was that water pump noisy. We went the whole season last year dealing with that noise. My wife kept telling me we should get a new water pump. I just kept telling her "next year".
So this spring, I got our camper all dewinterized just like before. But, I realized that I had not gotten the air purged out of the outdoor shower. Once I did that, my pump is less than half as noisy as it was.
That air in the system was the cause of all that racket.