ebee:

Well if you are using waste water or a river then why not?

I do not think your water supplier will like you using the public water mains though?

I would think they need WRAS approval. But if the property has a water meter fitted, which usually have a backflow prevention device fitted, there shouldn't be a problem with contamination of the water supply, which is their main concern. Even better if it was fitted from a tank fed source.

I saw this thread yesterday and thought of where we go camping. There are various washing up facilities and standpipes throughout the site all fed from plastic piping run from a huge tank at the top of a hill. I imagined I could fit one of these under cover of darkness in a secluded place near our pitch, and every time someone washes their hands I could be charging my phone. :)