Do I need 2 gaskets for a side overflow box bulkhead - leaking

[andrewkw]

I'm redoing an old tank, honestly last time after getting so frustrated I just ended up siliconing around the bulkhead until the leak stopped. Headed that way now but I'll give it another shot before it comes to that.

To be clear this is a side mounted overflow box. I have the gasket between the flange and the overflow box. There is no gasket between the overflow box and the tank. I've tried 20-30 times adjusting the tightness, scraping the inside and outside of the tank followed by rubbing alcohol and no matter what I get a drip. I wish I could remember how this was originally setup in 2009 but I'm pretty sure I only used one gasket then.

The hole does seem a little big for instance there is more play in the 1.5" drain hole (bulkhead not hole size) then then 1" return. I'm 100% sure I never used schedule 80 pvc so I'm not sure if this tank was misdrilled in 2009 or what. It did not leak originally way back then.

I have to cut the plumbing to add another gasket and order more parts ect so I figure I might as well post this before trying that. Some people love setting up new tanks but this is the part I hate the most. My next new tank I'll pay extra for bulkheads installed and leak tested

 

[pdxmonkeyboy]

The gasket goes between the tank and the box. No other gaskets are needed.

what is happening is that water is leaking through the threads of the bulkhead on the nut side of the bulkhead.

with the flange between the tank and box water can leak from the overflow or the tank but it wont get out of the system because it is trapped by the o ring between them.

Don't overtighten them or you can squeeze them and distort the seals.

 

[andrewkw]

Thanks Brian I will give it a shot. I have one extra new bulkhead so I can only try your suggestion or 2 gaskets, don't have enough to try both.