this is what you want to do if your on a budget and i feel this is the better idea anyways
this will work with 12 V
get TWO caravan sub pumps, around 20 L per min ( they cost about 15 quid each )
zip tie them as a pair and run 2 lengths of hose pipe ( also zip tie them together )
they can be wound on a reel
hose pipe is cheap enough from wilko's etc etc
you have upto 40 L per min, thus a fair amount of water movement
you can even have the cable from the pumps zip-tied to the hoses and then you can use your battery in the van to power the whole thing
wilkos are really cheap for garden stuff