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Re: Rebedding Water Tank Lid
Silicone was probably used because it is on every shelf and folks think it is the greatest stuff on earth. Of course if it is "bathtub caulk" grade, it contains arsenic to prevent mildew, not the best thing for a water tank.
Food grade silicone, neoprene, teflon...many ways to skin a cat. You might check with PermaTex or LocTite to see if they make a "Form-A-Gasket" sealant for water tanks. That's a product that is similar to silicone seal (to the casual user) but you apply it to a surface, like the edges of an oil pan, and then bolt it up and let it cure. At which point it becomes basically a custom made gasket, designed to be compatible with the fluid it has been used with.
I would think that tightening all the screws to a *very* similar torque would be more important, in the long run, than the specific gasket material. If you pick up a cheap "foot inch" 1/4" torque wrench, even the $10 ones from Horror Fright, that can give you a fast way to match them all up. Or use an electric drill/driver that has adjustable light torque settings, and use that.