Glue that withstands boiling water?

I’ve got a 3 litre “air pot” vacuum flask that I fill each day with solar-heated water. The plastic spigot into which the stainless steel dip-tube pushes has split, so the tube falls out. It’s not possible to tighten it up mechanically. I’ve tried epoxy - that turns red and disintegrates. I’ve tried Everbuild Stixall which claims to withstand 100°C and has lasted some time but is now going the same way. I’ve not tried Superglue because I read that that won’t work. Any other suggestions? Thanks.


Two-part epoxy resin. I used rapid - perhaps “normal” would have been better.

Just to add in case it’s useful for anyone: I’m trying silicone sealant (happens to be low-modulus neutral-cure). Probably poisoning me with what’s being leached out of it, but is surviving so far. I know you can buy special high-temperature silicone sealant which I have used to stick an oven door back on, but I wonder how different that actually is…