How much water stored, though... I mean, I'm reading 4 toilets per 100 men ( assume they are all blokes). So 13 toilets == call it 300 people.
Allow just 3 flushes/day per person, and just 6 litres/flush. 18 litres/day per person. And say only 100 persons after all.
That's 1.8 cubic metres/day. 18 cubic tonnes for a 10 day supply of flushing water.
54 cubic metres (tonnes of water) if 300 people.
Those of you who have read the plans, How big is the water storage compartment?