<a href=showthread.php?s=&postid=14962960#post14962960 target=_blank>Originally posted</a> by Entropy
Well everyone in this hobby (except me apparently) can get a 100% water tight seal on there bulkheads, but if you happen to be like me you could always put the bulkhead over the sump, so if it does drip a bit from time to time it will just fall into the sump. In the event of a power failure, I am willing to bet you will have much bigger problems long before the line drips enough to either flood the sump, or drain enough water from the line to jeapordize the pump.
As for your other concern, I don't think I would try this on an established tank. If you are doing it on an empty tank, just use fresh water to test and it will not be a big deal to drain, and refill if you need to.