I am planning a multi day hike in mid July, St. Cuthberts Way and St. Oswalds Way back to back, though not going onto Holy Island, so technically not the full Way! In preparation I went for a 2 day hike on Tuesday with full pack 11kg, and that was with 3 ltrs of water. As we know it was very hot, and still is. I used my water filter in several streams, and by 8pm I had ran out of water on the first day. Had to ask a house holder who was watering their plants to fill my water bottle, which they kindly did. I walked 30 mile Tuesday over rough terrain, the Durham Dales Challenge route! And 20 miles Wednesday. I arrived at Middleton in Teesdale on the first evening, bought some water, sat and drank it. I noticed how much salt was showing on my clothes. Mulled about it and came to the conclusion that water is only part of the solution, we need the essential salts and minerals. There is a condition called polydipsia, excessive thirst. It is also common in schizophrenia, where the person drinks excessive water, flushes out all the essential minerals. Can cause seizures and death!
So dont forget to hydrate appropriately. A lesson learned for me, and I should know better being a nurse.