What's the best way to make a waterproof solder joint?

[e1p3dr0]

Looking for your techniques on how to make a waterproof solder joint.

I've come across various different ways like liquid tape, self-amalgamating tape, silicone under shrink wrap, but would welcome your experiences.

[SuzyC]

Solder it. Coat it(optional) with (depending on high voltage/high-low temps/water pressure/flexing/saltwater/chemical environ): silicon grease/superglue --->double heatshrink with (optional)drop of adhesive/silicon grease/superglue under first layer heatshink tubing. Top heatshrink tubing should ~1-cm excess each side end of bottom heatshrink over soldering point.

[fordem]

My preference is marine grade heatshrink tube - this is similar to regular heatshrink tube but has a thicker wall and contains a heat activated adhesive that seals to the wire insulation and soldered joint.  I've also used the self amalgamating tape, but that does not work well on smaller joints.

[fourfathom]

A wire-to-wire joint?  Yes, the adhesive-filled heat-shrink.  Marine-grade stuff is available (ANCOR brand, for example), but you can also find it in most hardware stores as it is used when wiring submersible well-pumps.