Personally I don't see the need to carry all that water with you. A litre of water weighs a kilo, even if you do manage carrying weights well. Having only one fully functioning kidney I have to drink larger quantities than most, but I never carry more than 1 litre when on a multiple-day walk.
My walks are always in Snowdonia, maybe there's more water for refills available there than along the Penine Way, I really don't know? Even in near-drought occasions I've always found enough.
I carry it in a Nalgene Cantene collapsible bottle, much lighter than the solid one, and I make it safe with a Steripen Adventurer. When I stop for the night I fill a 5L folding water carrier like the one shown below from eBay. They fold in three vertically, weigh little, and can be slid down inside your sack. Just had to replace one, though, as it developed a leak and would empty itself overnight. That is enough for drinks (I have 500ml of energy drinks, from powder, evening and morning), water for freeze-dried food, powdered milk, coffee, and for washing myself.