You are not supposed to give pups distilled water. There are no minerals in distilled water and it makes them pee out the ones that are already in their bodies. Pups have actually died because their owners were giving distilled water.
Here's some info:
The possible health consequences of low mineral content water consumption
are discussed in the following categories:
• Direct effects on the intestinal mucous membrane, metabolism and mineral
homeostasis or other body functions.
• Practically zero calcium and magnesium intake.
• Low intake of other essential elements and microelements.
• Loss of calcium, magnesium and other essential elements in prepared food
from:
http://www.who.int/water_sanitation_...ineralized.pdf