Schnullidulli You mean having an air gap in the watertank by opening the lid? That didnt make any difference in the pressure buildup.
No I mean by having the lid only placed on leaving a space for air to come in as water left th tank…just in case?
the Max potential of an Ulka EP5 is almost twice what you are getting using the pump curves., but this is dependent on pumping into free air, not into a Gicluer (Group) get of 0.5 or 0.7 mm. It also considers no drag, or input impediments at all e.g. bore of tube, corner pieces, other fittings and flows. in other words perfect conditions… In your machine, the EP5 may have a significantly smaller flow rate.
Until you remove your case, you don’t know what pump you have, or model, is it fitted with a membrane regulator.
Next thing to do remove case, take a few photos, check for any kinked tubes etc..get pump name and code number, then we can look up the pump curves.
P.S. Mine is a prototype from 2019, so what’s inside may not be exactly the same as production models, with respect to the pump and other things.
P.P.S. To truly measure the flow potential of your pump, you would need to remove the outlet pipe and connect one onto the end of the pump and pump into a container.