Rainwater harvesting and the Water Regs

Have just come from a lecture/film about the chalk streams in Cambridgeshire and water use in new housing of which there is a lot. [Apparently the water abstracted from the aquifer lowers the water table so much that 20% of it has to be re-injected elsewhere to preserve the flow in certain chalk streams].

There is a big new development at Eddington on the W edge of Cambridge equipped with SUDS serving 8000 dwellings, the water is treated to render it suitable for non-potable uses (flushing loos, laundry) but the Drinking Water Inspectorate won't allow it to be brought into use.

I asked what the underlying reason is, I thought such systems at household scale had been available for many years, what is the real problem? No-one seemed to know.

Again, I mentioned our whole-house rainwater harvesting system citing 3 reasons it was not very practical for widespread introduction at the individual householder level:

• to get even the lower target of 80 litres/day per occupant you need about 50 sq m of roof per occupant where the rainfall is only 500 mm per year
• you need space for an underground tank
• it needs quite a lot of maintenance - filter changes, chemicals, UV lamps

but these issues should be addressable at the scale of a whole housing developments.

And again, I was told the DWI and/or Building Regs do not allow its adoption citing the difficulty of preventing erroneous cross-connections in individual houses.

Can anyone shed any light on the truth of this and what might be done to improve the position?