We were told the direction of the membrane itself was not as critical as it needs to be orientated the same every time it is installed. The cups are what is critical. I don't recall off the top of my head which way they are. I know the manual can sound a little confusing or seems to be lacking in this area. Read the section about cup orientation a couple times.
I am making a trip to our CDL dealer in the morning and will double check the orientation of the membranes and cups. They have been very helpful in the past to us.
Mike
Tapping since 1985 (four generations back to early to mid 1900s). 200-250 taps on buckets and then tubing in the mid 90s. 2013- 275 taps w/sap puller 25 gal. 2014-295 taps w/sap puller 55 ga. (re-tapped to vacuum theory) 2015-330 taps full vac. 65 gal, 2016-400 taps 105 gal, 2017-400 taps 95 gal. 2018-additional 800' mainline and maybe 400 new taps for a total near 800 taps. 2x6 Leader WSE (last year on it) supported by a 250 gph RO.