You have what looks like a 100-200gpd unit.
This will produce between 200-600 litres per 24 hour day, 8 - 25 litres per hour, depending on your input pressure etc.
Leave the valve closed for production.
The waste is meant to 'gush' out and the product will only be a dribble but it will add up.
Take a measuring jug and a stopwatch and see how much it produces in 1 minute, if it produces 130ml per minute then you are on the bottom end of the production range.