Is there still water in the system after 15 minutes on the pump? Of course.
Could water in the system by itself completely account for the observed rise in pressure? I don't see how it could, but I'm ready for someone who knows more about it to educate me!
Think about it this way. If one had liquid water present in part of a system, then evacuated the system, and then isolated said system from the vacuum pump by a valve (still with some liquid water present in the sytem), what would the pressure of the system be when equilibrium has been reached between water (liquid) and water (vapor)? It's a function of temperature, so consider it for a typical ambient temperature for Randy.
Of course, it's a fine idea to give the system more time on the pump and repeat the rate-of-rise experiment. Nothing trumps reality. We expect a report, Randy!
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