If you do bottoms trad obviously you will save water, I used to nip round the tops and the missus did the bottoms. I was at the end of the street before she had done a few houses. Its the fastest thing out there for many varying domestic houses. Or start at the back, round to the front, write out the bill and then do the back bottoms, you do get the odd drip though. So the less water you use the less to drip.