Free electricity.
If you're not on a water meter, simply fit your kitchen sink with a turbine and run the cold tap on it all day long, hey presto, free electricity.

Similarly, cover your lightbulbs with inwards facing solar cells to get free electricity to power your lightbulbs, it's kind of like perpetual energy.
(Universon, Tue 15 Nov 2011, 14:56, 2 replies)

This intrigued me....
But is it even practical? How much power could you generate from the flow out of a running tap?

A quick google suggests 14 l/min or 0.2333 l/s flow from a tap. That's 0.0002333 m3/s. Apparently the equation for hydropower is

P = hrgk

where P is Power in kilowatts, h is height in meters, r is flow rate in cubic meters per second, g is acceleration due to gravity of 9.8 m/s2, and k is a coefficient of efficiency ranging from 0 to 1

So, assuming a drop of 5m (from the attic tank to a ground floor flat), we get

P = 5 * 0.0002333 * 9.8 * k = 0.011445k

So even for a 100% efficient turbine we'd get about 11 Watts. Just about enough to run a single low-energy lightbulb.

Damn.

[Please feel free to challenge / correct / point and laugh at my work, here]
(moon monkey is busy making memories worth repressing, Tue 15 Nov 2011, 17:30, closed)

This sort of troll physics question just annoys me
My quick google came out even worse.

For the UK I found a typical flow rate of 7 l/min
If we use your 5 meter drop calculation and run the system through the most efficient micro-hydro unit I could find (running at about 58% efficiency)
you would get about 2.2 Watts which is cock all use to anyone.
( chuff monkey I AM him, Tue 15 Nov 2011, 18:27, closed)