Personally I find it hard to bring myself to add the weight of an extra water bottle 0.75kg on long rides, having spent plenty of time and money on getting my bike light and efficient. But I also know the engine wont function without water.
So, what to do! What is more efficient - stopping to refill or carrying the extra weight?
Last couple of long rides Ive done (Yorkshire dales cycleway and Fred Whitton route) Ive taken one bottle and been fortunate enough to refill from friendly locals or public conveniences. But yesterdays 75mi ride I was struggling to find anyone/where to refill, and didnt have my water filter for rivers/streams I passed.