Power showers not only hurt the environment but are also pretty vicious on your pocket. Turning the pump off will usually return it to being a normal shower.
A tip is to replace your regular shower-head with an aerating shower-head (from about £15). You simply screw the old one off and replace with the new one.
This device injects a bubble of air into the bubble of water, so it feels the same but uses 30 per cent less water. They do not work on instant electric showers, sadly. You can cut water use further by turning it off after wetting the body prior to soaping and then on again to wash it off.
From April to October this is how I shower using water heated by the solar hot-water panels on my roof. My washing gets even greener in winter, when the sun fades: I boil water from the rain-harvester in a copper kettle on my wood-burning stove. I then have a traditional sink body-wash.
The author founded National Carbon Footprint Day.