I was planning on buying a jet-pump (pump that pumps up water and puts in under pressure) which would be powered by a wind or solar energy. But some time ago i saw a thread here about energy storage in a water reservoir (water pumped up and let to flow back down through turbine). I'm wondering if it would be possible to put a reservoir of water on the attic (+/- 3 metres higher than where the toilets are located) and let the water of the drain pipes from the roof flow into this reservoir instead of the waterpit (well?). Or using a windmill to drive a pump instead of an alternator (no electrical losses) and pump the water in this reservoir.
Could anyone calculate the pressure (in bar or pascal) I would have if I would have a reservoir of 100 liters (big enough? too big?) that is elevated 3 meters high.
Is it something like: 100l = 100kg -> gravity-energy: 100kg * 9.81kg/N * 3m = 2943J 
this would mean that it would take around 3kJ to get 100l of water 3m higher, but it doesn't say annything about the pressure of the water...
