Bullet Black Tank Spray Failure

[RV802]

I have a 2014 Bullet Premier. Until this week, after draining the black tank, I have always hooked the dump station hose to the connector on the back of the trailer and given it a healthy dose of water to free up any waste that may be loitering in the tank.

This week when I tried to use the sprayer it was evident that no water was going into the tank. I closed the dump station faucet and when I disconnected the hose there was considerable pressure at the connection and water sprayed out as I loosened the connection.

We then discovered that water had come out of what looks like a vent valve under the bathroom sink.

I also realized for the first time that the outside connection doesn’t lead director to the black tank but, instead, connects to the plumbing system and eventually gets to the tank by a path I can’t readily follow.

I’ll try to attach a photo of the lines under the sink. The lower red arrow is where the pipe comes in from the rear of the trailer, the upper arrow is the device that leaked.

Any ideas as to what might be going on?

Thanks.