This smart shower flashes when you've used too much water

A smart shower head that flashes red when someone uses too much water is aiming to make people think seriously about water conservation.

Developed by French firm Start & Blue, Hydrao has built-in LED lights that change colour as more and more water is used. Once a 50 litre limit has passed it flashes red to suggest it might be time to get out of the shower.

The system works with a companion app, available for iOS and Android, to let users track water use over time with further options to change the water consumption threshold and what colour the shower head flashes.

The first generation, which sold around 1,000 units, reduced water use by an average of 25 percent, according to the company.

The technology, which was first launched on French crowdfunding site KissKissBankBank in 2014, is now on its second generation. The new version, shown for the first time at CES 2016, will debut on Kickstarter in September before going on sale in February or March next year for around $99 (£67).

Hydrao can be fitted to any conventional shower hose and doesn't need a battery, with everything powered by the flow of water through the shower.

The shower head connects to the companion app via Bluetooth 4.0 and stores data on 200 showers to let users track progress over time. While the average shower uses around 80 litres of water, Hydrao aims to cut this down to around 55.

To achieve this, the LED lights built into the shower head change colour throughout, starting at green for up to 10 litres, then blue after 10 litres, red after 30 litres and flashing red after 50.

Marketing manager Thomas Ciezar said that the technology was ideally suited to teaching children about being smarter with water, but could also be a money saver for households.