Hi, recently bought EC.4 and I have few questions whether it's normal and expected from this pump. Sorry for possibly stupid questions My old vacuum pump is oil-less so I'm kinda new to this pump.

Pump was filled with oil which came with vacuum pump up to half of the sight-glass.

1. When pulling vacuum oil vapor separator looks like this. It settles down as soon as full vacuum is reached. Is it supposed to work like that? Catch oil and collect it in the container?

2. When full vacuum is reached oil has lots of air bubbles. They disperse when pump is off. Is it normal?

3. What is the purpose of return check valve? I thought it was supposed to hold vacuum when pump is off. But as soon as I switch pump off - vacuum gauge drops to zero and you can hear air being sucked back to the vacuum pump through oil mist separator. So is the valve for holding vacuum or just for keeping oil getting sucked back into the tubing?

Thanks

Non return valve seams to work when pulling air with mouth. But as soon as I assemble pump no matter how hard i pull, diaphragm does not move up. So I've fitted compression spring (14mm dia. 7mm height). It fits perfectly in the hole and pushes the diaphragm up. After switching off the pump - vacuum dropped by 0.08bar in 20mins and was stable for 8 hours. So far really happy with the pump. It's really quiet!

I'd rather not send the pump as I'm from Lithuania and the shipping back and forth will get quite pricey. Also a bit worried about getting parcels after Brexit 

Anyway thanks for looking into this!