Holding Tanks

[ricknnell]

I know there's a drain water hose with a valve on it, under the fresh water tank, but there's 2nd one 2foot from it,,,, what is it for?

[MichaelA]

One is probably the fresh water tank drain, and the other is probably a low-point drain.

Pic could help.

[travelin' texans]

Or the fresh tank vent.
RW ran the vent underneath rather than use the little screened port next to the fill port. Some added the valve to the vent as it would siphon the the fresh water out through the vent.
You need to make sure if it's the vent with a valve it should be open when filling the tank to prevent it from pressuring up.
The low point drains should be red & blue lines with caps or valves.

[Scraper]

On mine, one is the fresh water tank gravity drain, and I believe the refrigerator supply line drain (it pressures up with the pump on or on city water.

[rtoon]

On my 2013 it’s an overflow drain