Rainwater Collection

Hi there,

I recently bought a house in Valencia which has a small piece of land.  I'm interested to know if others have gone down the route of installing water collection systems which provide rainwater to sinks, toilets, showers etc.  I'm thinking of getting an underground tank to facilitate this.  Does anyone have any advice or experience to share?  Could anyone recommend a company that can install, sort out the drainpipes and the plumbing and electrics all in one go?

Many thanks