I happened onto this a while ago.
This is a DIY manometer for testing and adjusting LP gas pressure:
RV U Tube Manometer
This is a DIY manometer for testing and adjusting LP gas pressure:
RV U Tube Manometer
Thanks for this post. My refer wont stay lit on propane after a few minutes and the service manual gives specs on water column pressure but until now I didn't even know what that is. I will give this a try.
Larry