Overflow can wiggle, bulkhead loose?

[NancyFish]

My overflow is sitting flush & bulkhead screwed on hand tight (tightening more feels like pressuring the box) — but they still have a slight wiggle?? Looks like the bulkhead flange can lift up a smidge, maybe enough for 2-3 sheets of paper?

I’m afraid to tighten anymore at risk of cracking the tank. Am I doing something wrong or is it okay for the wiggle?

Brand new to plumbing, have the aquarium drilled and a 12” overflow hanging by two 1.5” slip bulkheads with two gaskets each. The back is painted a thin layer.

— Side question, I trimed one of the bulkheads 1/4” more than I would have preferred. The gaskets & nut screw on enough where it feels tight, but the bulkhead could probly use 2-4 more threads to reach the very end of the nut. It feels fine, but could this be a leak problem down the line?

 

[Sassafras]

If you can move/wiggle the bulkhead, it is going to leak. The painted back probably isn't a problem if the nut is on the outside and the gasket on the inside against clean glass. Picture would help on the trimmed neck question.

 

[NancyFish]

If you can move/wiggle the bulkhead, it is going to leak. The painted back probably isn't a problem if the nut is on the outside and the gasket on the inside against clean glass. Picture would help on the trimmed neck question.

I can get a picture of the short nut later.

Would I keep tightening until there’s no wiggle?

Just feels tight already which makes no sense since I can move it and it can sit flush.. I’ve read so many people cracked their tanks over tightening but maybe that’s thinner glass?

 

[Sassafras]

Unless you're extremely strong, I don't think you could hand tighten the nut enough to break glass, at least not if it is 1/4" thick or more. Don't use a tool just yet. Most advice I've heard is hand tighten as far as you can go and then go 1/4 turn more with a wrench. You want some compression of the gasket.