Analysis by UK Water Industry Research (UKWIR), collating the findings of 44 separate studies found these to be the most cost effective and sustainable measures for water conservation.
Other measures included rainwater harvesting, washroom retrofits and low-use showerheads, spray taps and urinals.
The results coincide with the launch of a new water efficiency website from the Bathroom Manufacturers Association. As the majority of water used in the home is in the bathroom, this site could play a major role in encouraging people to take water efficiency seriously.
Pamela Taylor, Chief Executive of Water UK said: "Last year was very dry with only around 40% of the average rainfall and if 2006 is similar we must expect additional stress on water supply systems and the water environment."
"The water industry is delighted by the responsible action taken by the Bathroom Manufacturers. We would recommend anyone looking to install a new bathroom to visit the new website first. They will be able to make choices that help the environment and the public water supply in the future."
Water UK said it expects the new site to play a major role in reducing water wastage in the UK.