SunPump comes with a Schrader Valve installed on the larger of the two service valves to allow adding filling, like a car tire. They are one-way, so it is essential fpr the HVAC Mechanic to remove the Schrader valve to do an evacuation of the line set and panels. Later he will put it back in, when the evacuation is complete.
If SunPump arrived with proper pressure on the Gauges, it shows the original Schrader were perfect,, otherwise a leak would result in the gauges being at zero after many months between factory fill and install dates. If you find a leak at the brass service valves weeks or months after startup, it is on the HVAC mechanic, he was the last one to remove and replace it.
Best practice is to put in a new Schrader after any removals past the first one, they are cheap. Customers do not mind paying for a new SV, to eliminate the risk of a leak. If it leaks, the HVAC person will need to suck it up for his mistake. Leaks outside of the SunPump case are the installers issue to check for leaks and repair if they do leak.
Go to 2:40 to for about 30 seconds on the Youtube video below to get the essence of Schrader replacement from a career HVAC Pro, now retired to teaching.
https://youtu.be/Ly9fgu0rv0A?list=PL8sVu1Tuzuf3hvqorik-43OrDQodlMNKy