If this is inside the tank put a plug inside AND outside if possable. If threaded use silicone on the threads instead of plumbers tape as it seals very well. on a slip I agree to glue it in place again on both sides if possable.
hrmmmm not use a sump? What about using it for a closed loop?
Hey I just noticed you had a post that you were using an overflow and it was really loud.
check this out... build a durso.. seriously.. nothing else pop into Home depot and get the stuff...
Another tip is to drill a hole in the top cap of the durso and run vinyl tubing into it and down... and zip tie 7-8 foot of it... it'll be inaudible because the pitch is lowered so much.
We'll help you out man... no need not to use an overflow because it is loud. I learned quick how to fix this when the wife was angry at me because she couldn't hear the TV in the living room.