I have the Easy Composites resin infusion starter kit with the VP425 vacuum pump. My vacuum gauge is reading min. -27 even if the hose is clamped. In the video tutorial, it was reading -27 and he said “it should be reading -30... well, nowhere near... there's clearly a leak”. I know there is no leak because it stays -27 for hours.



To narrow down issues, I bought a new vacuum gauge and this one reads -29.



Do you have any such experience? Do you think the vacuum pump is working properly?

Those vacuum gauges are more an vacuum indicator than accurate measuring tools. The pressures you are aiming for during an infusion are far beyond the accuracy of these gauges. If the bag is leaking, and it is not an huge, easily located leak, we are talking about 10mbar (0,3in hg). This would already be hard to see, but the tolerances make it even worse. As you already discovered, two gauges show different results.
Without investing in a digital tool, you have to aim for "maximum" vacuum, whatever this means for your gauge. If you are sure everything is without leaks 27 might be your new 30.

Three tipps:
-The cheaper pumps, like yours, change their sound, if your system is (almost) leak free.
-where did you clamp the hose? As you claim that it holds -27 for hours, I guess you clamped the hose to the pump. Maybe your connection to the pump is not perfectly air tight.
- did you open the little rubber cap at your gauge? If not, this might be the problem.

Thanks for letting me know I don't have to buy a new vacuum pump