Fix for a leaking marine fuel tank?

[elkinrutdrivemenuts]

So I got a new fuel tank for my boat and apparently I did not get the memo that there is a common issue with these new tanks, they leak!  The new cap designs do not allow them to vent properly?   If there is any amount of gas in the tank, it comes out the pickup assembly.  I have already returned and received a new tank, same issue.  I was told to add Teflon tape to the threads, same issue.  I did a google search and found out this seems to be a common frustration.   Any modifications I can make to allow the tank to vent properly?

Edit: Tank is a 12 gallon portable tank. 

[KFhunter]

What are we talking about here?  A portable 6 gallon tank or a 60 gallon tank under the flooring?

[BD1]

  however...either way I would never keep a tank that leaks. A brand new tank certainly shouldn't and I would continue to return it until you find one that doesn't. Honestly after the second return I would be looking for a different manufacturer. 
Good luck and be safe

[CP]

Victim of the 2009 EPA regulation on venting fuel tanks?  If so, your fix could be as easy as drilling a hole in the right spot. 

[elkinrutdrivemenuts]

Victim of the 2009 EPA regulation on venting fuel tanks?  If so, your fix could be as easy as drilling a hole in the right spot.

That is what seems to be the issue.  My old tank was from 2006.  Now where might the "right" spot be?  From what I have read, the vent cap doesn't vent as well as it did back in the day.

[KFhunter]

Well I'm guessing this is a permanent tank under the flooring,  I'm out.  My advice is not drill holes in tanks, and use a professional installer, and get a non leaky tank. 

And I've installed a lot of factory tanks in new boats

[elkinrutdrivemenuts]

Well I'm guessing this is a permanent tank under the flooring,  I'm out.  My advice is not drill holes in tanks, and use a professional installer, and get a non leaky tank. 

And I've installed a lot of factory tanks in new boats

I updated the info, its a 12 gallon portable tank. 

[deerlick]

i had the same problem with a portable tank, my solution was to just crack the cap loose a tiny bit and it resolved it for me.

[CP]

Tanks aren’t allowed to vent any more.  The new ones have a valve that allows air in, but not out.  So, they blow up like a balloon when they get warm.

You can loosen the cap until it breathes.  Or you can add a vent (see link).  Find a place in the cap that allows a drill of the right size then add the vent. 

I’ve done this to all my “new” plastic gas cans that were manufactured after this idiotic regulation, so they don’t go “glug glug glug”. 

https://www.amazon.com/gp/product/B00ZQ10FWG/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

[KFhunter]

Just type in your tank brand on google and buy a vented cap from amazon, lot's of universal vented caps on there

[CP]

Nothing like a pressurized gas bomb in your boat.

[elkinrutdrivemenuts]

Thank you for the responses.  I will try a new cap and see if that solves the problem. 

[BigGoonTuna]

A little off on a tangent here, but I bought one of those “demand valves” that go inline between the tank and motor for my old boat when I got an “EPA” tank. I started having carb trouble or so I thought. Turns out the valve wouldn’t fully open and my motor was starving for fuel at WOT.

These valves are supposed to keep a pressurized tank from flooding your outboard, I would rather disconnect my fuel line every time than ever put another one of those stupid things on again.