Jun 21, 2018 - 4:08 PM
Welcome to MySwissAlps. I would advise each of you to have 2 liters of water at the beginning of each day. And grape sugar tablets. You are of course well trained and in good condition.
Then, it depends if you are with a group (and thereby obliged to keep on the trail), or if you can make some diversions. Which one is the cabane that doesn't provide drinking water? Do they sell bottled water?
Maybe you have already found out, but broadly it looks like this:
Day 1 Bourg-St-Pierre - Mille: In BSP, otherwise unlikely to find water
Day 2 Mille - Brunet: unlikely, but maybe at the hamlets towars the end of the trail
Day 3 Brunet - Panossière: Unlikely
Day 4 Panossière - Chanrion: at Mauvoisin, a little distance off the trail
Day 5 Chanrion - Champillon: At Vaud and Ollomont
Day 6 Champillon - St Rhémy: At St Oyen (if that is on your trail)
Day 7 St Rhémy - BSP: at Grand St Bernard Pass.
Good luck! Should be a fascinating tour!