T&T: Stainless Steel Fresh Water Tanks

[Michel Girard]

Good morning all - 

I have three fresh water tanks on my trawler.  For some reason, that I can't
locate yet, they expand when filling and contract upon use.  This causes a
loud banging sound.  My air vents appear to be clear and run in a relatively
constant uphill direction.  

As a result of this, a few of the welds along the seams have failed.  I
don't believe welding in place is an option because of location plus I would
really like to not have to cut another access hole.  Does someone have a
recommendation of a material I can use on the outside of the seam to plug
the leak?

Another other thoughts on my expanding/contracting/noisy water tanks would
be greatly appreciated!

Michel
Angle 60'
Seattle WA