Black tank check valve in the fresh water system?

[grantmnc]

While investigating the source of water dripping down the bottom of my 2017 Holiday Rambler Endeavor 40E, I found the source to be the part pictured. It is a Swan industry part that says "FOR BLANK TANK USE ONLY". It was wrapped in about 2 feet of electrical tape. When I look at the plumbing diagram I got for the coach from REV, it clearly shows this part plumbed to lines going into and out of the top of the fresh water tank.



In the mean time, I have just put a right angle elbow in it's place. It helped me confirm that this check valve was indeed the source of the dripping water.



My questions are:

1. What purpose would this check valve serve in the fresh water system? I was thinking it was to allow air to enter the tank when the pump removed water, but the lines are filled with water. My tank is about 2/3 full.
2. Would it function at all with tape wrapped around it?

Thanks in advance for any assistance.

[Ljwt330]

That is indeed a Swan vacuum breaker designed for black tank flushing systems.

Can you clear up some things? Are those two blue pipes both inserted into your fresh tank, as you described? Are you sure the one on the right is not outside the tank?

Also, are you sure they enter the fresh tank? Could they be passing through a plastic cover separating the basement from the coach and are actually part of the black flush?

Note the vent pipe at the left. That is likely from the black tank which must be close. Fresh tanks are generally a translucent white.
N