boris have you got the gutter down pipe running into the aco drains.im looking at building something similar myself this summer.
im thinking off running a lengh of sink waste pipe the lengh of the block where the floor meets the bed box but a few inchs up with holes drilled in it and linked up to a water butt so basically turn the tap on and water spills into each block.then sweep out.saves fecking about with buckets or hose pipes.then use 1 of these floor squidgys