The city water connection on both of the Valterra units I mentioned is brass. Only the fresh and it's sister overflow connections are plastic.
I had to pull the sofa away from the back wall and take apart one of the armrests for access.
2005 Cummins 3500 2WD LB quad cab dually pulling a 2014 Blue Ridge 3025RL
ValterraParts.com has tones of information on all their parts with videos explaining how the parts work and which model is best depending on your situation.