Gardners have been urged not the pull the plug on used bathwater but instead to use it to water the garden.
Rachel Fletcher, head of water services at regulator Ofwat, told a committee of MPs on Thursday: "The idea of using treated drinking quality water to water our gardens and wash our cars in the 21st century just doesn't seem appropriate."
As the UK recovers from a record heatwave that saw people being urged not to waste any water over fears of a hosepipe ban, Fletcher also said rain butts and rainwater tanks could be a good idea (for collecting water when it is raining).
With the weather set to pick up again over the weekend, hitting 30 degrees celsius in some parts of the country, repurposing water might be a good idea.
The RHS says on its website that most gardens are hardy enough to be watered in moderation with repurposed water - known as grey water - even if it does have soap and suds in it.
"Grey water should be used with care, but can be useful in times of water shortages," it explains. "Plants can be watered with shower, bath, kitchen and washing machine water - fortunately, soil and potting composts are effective at filtering them out."
It continues: "There should be no problem with small-scale, short-term use of grey water to tide plants over in summer drought. An exception is on edible crops, due to the risk of contamination from pathogens in the water."
It does add, however, that long term use should only be considered after seeking expert advice and that it should only really be used in an "emergency".