Again, I posted this before but just think about this. I also use a vacuum pump and it's great, convenient, and limits the exposure of air/wine. But remember.. these were aspirators and may have been subjected to less than clean air. The problem arise when you shut the pump "off". Any vacuum, anywhere will will equalize. You don't want atmospheric air entering the carboy via reverse through the pump. That will allow clean air to pass through the pump valves, pump oil, (yes all these pumps have oil in them and not mineral oil), and reverse through all the ports this aspirator has been subjected through it's entire life. You must think comfortably on how you want to handle the transfer after the vacuum. My suggestion is to install 2 ball valves (1 between the pump & receiving carboy, & 1 between the two carboys) this way you can stop the vacuum and re- pressurization via the pump. The other valve will allow you to stop drawing from the transfering carboy. This is helpful as when you even shut the vacuum, the transfer will continue for some time or until you have an equalized pressure. You want to stop transfer so you don't suck the transfer carboy dry and then pull in straight air and bubbles into your newly transfered carboy. Once you have your new carboy full, and if there is still a vacuum in it (which it will) the gasses in the wine will usually help if not completely equalize the carboy internal pressure, so now you can remove the the rubber stoppers and hoses. I forgot, I also have a small vacuum gauge inline also so I know the status of my carboy. My main reason again for this post is "Don't let the air from the pump return to your carboy!".