ORIGINAL: Ed
ORIGINAL: George
No, leave it full. If you want to drain your tank/s, do it from the UAT fill line and it will draw all the fuel from your tanks while leaving the UAT full.
George
But George, won't using the UAT fill line also empty the UAT ?
Only if your fill line is at the bottom of the UAT. Once your tank/s have emptied, the line from your tank/s to UAT will be dry and sucking air and in turn, the fill line will no longer be able to suck fuel, leaving the UAT full up to the point to where the fill line is located.
Suck the fuel out using the fill line and you will see. NOW, if you drain from the pick-up (the line feeding the fuel pump), that will drain the UAT; this may be where you are getting confused. I hope I didn't confuse you more.
George