Medical grade de-ionised water has (almost) no dissolved minerals in and isn't conductive.
You should be able to submerge your pc in it and still run, like the did with oil/coolant ages ago.
Not sure how stat. consumer warranties work in the USA, but in AUS, you could argue this is a major fault (since it killed your computer), which would allow you to get a refund, not a replacement.
Your next system maybe use an air cooler or better brand water.
Hoses shouldn't just be glued. They should all have compression fittings.