Street Water Mains

[pullgees]

First of all I know nothing about the technical side of things - what is need to turn a turbine even a small one - so feel free to rubbish my suggestion.

Is it possible to install water driven turbines in street water mains in the street? I don't mean in the home. Apart form night time, the water flow in a street water main is practically non-stop. Maybe the Archimedes screw method could be used. Then feeding the electricity back into the national grid.
But as I said I haven't a clue about the psi or flow rate that would be required to make it worthwhile.

[QuarterPole]

This would be like putting a wind turbine on a car. It would add drag to the system and decrease the efficiency. Any energy that was collected would add to the load of the pumps on the supply end, or if the supply was gravity fed, would decrease the throughput.
Unless, of course, some sort of OU vortex turbine/pump can be demonstrated, which would be awesome.

[pullgees]

You're absolutely right, shows how much I know.
But why aren't flowing waterways being used? I don't mean huge seven estuary type projects in every river, interfering with shipping and wildlife. Why not smaller ones installed every mile apart say, something on the scale that is going to power Windsor Castle or ones which are of the correct scale for each river. Up to 150 years ago there were water mills all over the country producing enough energy for the mill and probably some to spare and they were just creaky wooden wheels.