Installing a drain valve

We have an outdoor sink that I would connect to with a hose, this year I wanted to add hot and cold water lines to the sink and get rid of the hose.

I drilled 2 holes in the floor (after triple checking the area!!) cut the lines added the fittings using a pex tool and pex fittings. Didn't take but an hour to do, so I think you can and should add the low point drains. It is a good idea to be able to drain down the pressurized lines when the temp drops. JMHO

OP here.

What I am doing is not for winterizing, but so I can us it in fall and spring when temperatures can go under 0 overnight.

I have a 1999 Rockwood Ultralight 26'

My 1990 Winnebago has 4 low point drains. They drain the system so well that compressed air does nothing afterwards, so I no longer bother. I also do not use antifreeze, except in my p-traps, of course.

You can get a transparent end coupler with a hose connector. Just leave the end cap on and you can use that valve.

Most RV's have 2 low point drains.1 hot 1 cold. However some don't have them. My 2011 Keystone Sprinter with the Thermo Package installed does not have low point drains. The only penetrations below the plastic belly is two 3" drain valves and the FW tank drain. When you think about it, if using pink antifreeze there is no need for low point drains.

You are correct. Your FW tank is not pressurized.

List your trailer information (make and Model). Somebody on here will be able to point you to your low point drains. But like Craig said, opening those drains alone may help but it will most likely not prevent things from breaking.
Some use compressed air to blow out the lines successfully. Some of us will just pump RV anti-freeze through the system.
Don't forget to drain your water heater and then bypass it if possible (search "water heater bypass" on the site). This will save you a lot of anti-freeze.
Also make sure you run it through every valve/faucet in the trailer. The toilet and outside shower systems are often forgotten.

If you have any neighbors with RV's it would be a good idea to ask them for help if you have never done this before.

Easy to do, however you should have low point drains that will do the same thing. Just opening the drain valves will not stop the pipes from breaking in winter. You will still have to use the antifreeze to keep things safe.