What is this black valve?

[Philip Jones]

I am (sadly) winterizing my trailer today. I know the top valve (green) is the winterizing bypass valve, but what is the black one (red)? Is this one involved in winterizing?

If not, what is the appropriate normal position for this valve when using the trailer, and what purpose is this valve? Thanks for any help!

[sheriff1]

I believe that is a low point drain.

[Alumaholic]

Low point drain.
Keep it closed when the Airstream is in use.
Open it when draining water from the lines.

[Philip Jones]

Thank you! So, this low point drain drains low-lying water in the water heater to the low point drains on the outside of the rig?

I presume the closed position is when the notch is 90 degrees from the direction of water flow?

[SteveSueMac]

You may find it’s a water heater low point drain that empties directly underneath the valve - that’s the case with mine (2012 27FB). I found it first season after it was winterized. I’m filling things up and trying to get city water to fill the water heater and there’s a massive flood outside under the water heater. Turned that knob to close it and all was good.

[polarlyse]

Just to throw a wrench into the pot here. Follow the pex line and see where it
comes from / goes to. I found an in-line valve on mine that served the toilet supply line. Something we can turn off if I need to remove or service the throne. If it has an outlet that drains through the floor then more likely to be a low point drain.