Have you looked in the outside water connection compartment? It may be behind the panel at the top. Have someone turn it on and off while you track it down by sound. Good luck and let us know what you find.
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7