I'm sure will Gary from airwaterice will respond soon. He's been very prompt with replies to my questions even before I ordered my unit 2 months ago.
I have the same unit. It's rated for 100 gallons/day.
Do the math. That comes out to a little over a cup a minute. Your pressure is below the 50psi recommended minimum and you're getting just under 50% output. The following is directly from the web page for this unit:
"If you have fifty degree water at ( 50 ) p.s.i. expect half the rated production"
My pressure gauge reads between 50 and 60 when it's hooked up. It takes a few hours to make up about 15 gallons of water for my water changes. As I got mine before he included the automatic shutoff I have to remember to keep checking when it get's close to full. If I get distracted I end up with a very clean floor