Where Did The (Great Flood) Water Come From And Where Did It Go?

In the thread "Evidence for a recent flood", claims have been made as to the sources of the water of the flood, the "fountains of the deep" amongst other sources.
Arguments have been made that the flood was not catastrophic or violent, that water flows uphill, that the opening of the fountains of the deep doesn't mean water reaching high in the atmosphere, that water wasn't in the mantle pre-flood, but got there afterwards when the "single land mass" divided in the days of Peleg.

So many different arguments have been made, some inconsistent with others, that it's difficult to visualise the floodist's model and the various statements are scattered over numerous posts and threads.

In the distant past we've discussed this topic, touching on Walt Brown's hydroplate theory and vapour canopies etc, but it would be worthwhile to discuss this subject in light of the ongoing thread "Evidence for a recent flood". In that thread many claims are made regarding the source of the flood water. Discussion of that would be off topic in that thread (I think) and it would be useful to have all the claims together in one thread.

Assuming you would like evidence for where the water came from and where it went, I don't think this would be off-topic for the Evidence for a recent flood thread.

It's not so much asking for evidence as asking for the "models" proposed to be examined for plausibility with regard to current science.
In the thread "Evidence for a recent flood", the source of the water is claimed to be the fountains of the deep. As far as I can tell, these fountains resulted from the release of water from the mantle (so the argument goes).
A rough calculation puts the amount of water required to flood the entire earth at 2046 million cubic km. To help get an idea of what that means, the Earth's crust is estimated to be 1332 million cubic km (I googled that). The temperature of the mantle ranges from 1400C to 3000C with densities ranging from 3.4 - 4.3 g/cm2.

What effect would 2000 million cubic km of superheated pressurised water have on the atmosphere, crust and life if it was released to the surface over a period of 40 days? What sort of atmospheric temperatures are we talking about here?

When water becomes steam it increases in volume by 1600 times, giving us a total of 3.2 million million cubic km. In contrast, the earth's atmosphere is estimated to be 51,000 million cubic km so the volume of steam is 62.7 times the volume of the earth's atmosphere