White Water Supply

[Queen_n_her_goat]

Anyone know the exact function of the white lavatory supply tube? Is this for the pump side? Cannot figure why there is a standard blue and red pex and also white pex supply and apparently white pex return on my bath lav.

[flybouy]

That's likely your black tank flush line. Follow it up to its apex ( typically behind the sink bowl) and there should be a vacuum break valve that prevents the black tank contents from going back into the hose connection.

[Queen_n_her_goat]

That's a bit puzzling as one white supply actually goes into the faucet with the cold (blue) line. I would expect cross contamination if that was the case.

[chuckster57]

Originally Posted by Queen_n_her_goat

That's a bit puzzling as one white supply actually goes into the faucet with the cold (blue) line. I would expect cross contamination if that was the case.

I bet if you look closer the white pex may be zip tied to the blue pex, but they are not connected. If they were your black tank rinser would run constantly.