Fresh water drain keystone alpine

It should be under the trailer some where . Mine is just a 1/2 shut off under the front. You can just see it attached to the pex pipe

Try looking on the left side just behind the axles, took me a while to find it.

Don't have an Alpine, but my Keystone Montana has a small pipe hanging down a few inches with a white plastic cap near the rear of the trailer. Remove the cap and it drains the fresh water tank.

I will check those places when I get home tomorrow

Just as was said before I have had 3 Keystone Montana's and I would think Alpine would be the same the drain pex tube is hanging underneath behind the rear axle with a white cap on it ,in the future it might help ya if ya joined the Keystone owners Forum http://www.keystoneforums.com/forums/index.php and they would tell ya EXACTLY where it is,The Montana owners forum has helped me A lot and I think the folks at the Keystone Forum would know just about anything about your Alpine