after being in the merchant marines for about 15 years, I have seen chiefs that swear the only thing that will work is the very stuff the previous chief swore wouldn't work. That includes just about every type of sealant you can think of, teflon tape, teflon paste, rector seal, aviation permatex, permatex #2, loctite, and whatever else you could find. And the only thing that was consistent is they all worked. And given you only have 7 PSI at the most. You could probably use biscuit dough for that matter