Navion 24V water flow
When connected to city water, all faucets, shower, etc. flow normally, and I can step on the toilet flush to fill the bowl normally. However, when I press the flush fully, I hear a vibrating, sort of a growing noise under the coach, maybe under the shower, for about a second, then my water flow in the toilet and other fixtures goes to a trickle (both hot and cold). With no fixture flowing, I can wait 20 seconds or so (I suppose until the trickle restores line pressure), and normal flow is reestablished.
Everything works normally when using the fresh water tank and pump.
I've studied the plumbing diagram, and assume it's a faulty check valve or something, but really don't know where to start.