This device fits in the water cistern of your toilet and is filled with water causing it to expand and displace volume in the tank. This means that every time you flush the toilet, less water is used.
Dual flushing systems for toilets give you the option to use a smaller amount or volume of water per flush instead of the full flush volume all the time, so you can save water. Most modern toilets are fitted with a dual flush system, but they can also be retro-fitted to existing systems.
Some showers can use a lot of water, particularly power showers, so by spending less time showering you can save water. You can use a shower timer to help calculate and reduce the time you spend in the shower.
An aerator tap or showerhead pumps air into the water flow, which reduces the amount of water you use for the sink or the shower.
These water saving devices are available from DIY stores or garden centres. You can contact a plumber for advice on what water saving devices are suitable for your home.