A craft with one Kerbal and a Water Purifier has a positive production of pure water.

[Sirplentifus]

After opening my save, I did not change any of the values for the consumption rates, etc. that were suggested.

I noticed that a craft working with a kerbal and a water purifier continuously present and active, produces water, instead of having a net consumption, or at least a constant amount of water...

[ntwest]

Pretty sure that there is water in the snacks that the Kerbals eat (food). That could be why so see more water than you brought.

[Sirplentifus]

I disabled food and oxygen, and water was still being produced.

Although, since I was on Kerbin, I think disabling the oxygen didn't change anything.

So I also tested this in space, with oxygen and food disabled, and water was still being produced...

[ntwest]

Maybe kerbals just generate all of their outputs each second regardless of inputs?

[Sirplentifus]

Which would be an issue too. But I don't think it makes sense that consuming food outputs water... I doubt that's what's happening. What I think is the most likely case, is that either Kerbals produce more waste water (in weight) than they consume, or the purifier produces more water than the waste water it consumes (in weight again).

But I have yet to look at the numbers...

[taraniselsu]

If you think my numbers are wrong, please look over my spreadsheet and check out the sources, and show me where I messed up.

Sirplentifus is correct that there is some water in the food. It is not completely dehydrated just like the food currently being consumed on the ISS is not completely dehydrated. See my sources to see where I got that from.

[Sirplentifus]

Well, I noticed in your spreadsheet that Kerbals (and apparently humans too) produce more waste water (both in L as in Kg) than the ammount of fresh water they consume.

However I remembered from my biology classes (after reading the "metabolic water production" in your spreadsheet) that our cells actually produce water when processing food. So I guess there is in fact always some water in food... So even if the food was completely dry, there would still be more water being excreted than consumed.

This means that I don't have to provision any water in my space travels, if I take a water purifier, and a minimal amount of water with me. Is this realistic?

Thanks for your attention.

[ntwest]

Water is a good dense source of O2 as well!