expontaneous cold polluted water

If you dont pick mined ice tile up, it will slowly thaw and melt on its own. Also check the cieling above where it keeps happening, and see if you have pH2O ice blocks above it melting on their own and dripping down.

This is my best guess:

You are checking temperature of the output, not the input of your refinery and using polluted water which boils into steam at 246F. You are checking it at 155F. There is, on my screen anyways, an 80F difference in the input and current output temp when refining Steel. You have roughly only 11F various window from going to steam. If your automation is not perfect, it will let pockets of really hot PW through the system.

I'm guessing you refined Steel with that setup and it's trying to find the lowest solid block beneath the burst pipe.

Pic below to demonstrate:

Edit: I let it run another cycle. There is roughly a 92F increase between input and output temp. 155+92=247F, which is 1F over boil.

For now, you could drop your filter temp down 10F or so, but I would scrap that system and start filtering it from the input, not the output. You wanna catch the damage before it is done. Well, you probably don't want too hot of PW laying around anyways, but maybe also add an input filter system as well as a safety and keep the output filter as well, but at a safer temperature.

Edited May 3, 2019 by tommytom2k2