No batteries required,. just add water

Woohoo!. Concrete poured no problem. Was able to get mixer lorry reversed right up to site,75 litres of water added and whoosh!! stand back and let it flow in. Whole job only took half an hour, should be able to start building next week.
Might give this old water level a dusting down and give a shot again, all the new laser ones are great but they don't go round corners or from room to room and are pretty accurate, so long as no-one stands on the hose.