Rainwater for toilet flushing

[LucidEnergy]

Is there anywhere in the world that commonly uses rainwater for toilet flushing? I know that seeing as it is greywater, it is suitable for toilet flushing, but I've never known it to happen in England. But I thought in more arid places this might be something that is more common.

[allegrif]

This sounds like common sense to me, and I think it should be a legal requirement in new buildings. For example, I think a large block of flats or a large commercial building/skyscraper should have rainwater collecting facilities built in, which can then feed the toilet plumbing. In fact I don't understand why this isn't widespread already, surely it would save everyone money?

[LucidEnergy]

Using it in a block of flats seems like a good idea. There could be a separate grey water tank which provides free water to people's toilets, in addition to the metered clean water they use for other applications.

[St Rhenium]

I agree. Having separate plumbing systems in older buildings might not be feasible, but there is absolutely nothing stopping them being designed into brand new buildings. It's almost treacherous that this isn't widespread already.

[JamesH]

I don't think it would even be that hard for older buildings, just one more pipe coming down from the gutter to a tank, then to the cistern. Maybe there are things I haven't considered but it doesn't seem too much hassle.