David Wilkes, who created the Interflush system which fits into a handled toilet cistern to save water, said he has updated the design to make it easier to fit and completely sustainable.
The Interflush system fits into the existing siphon in the cistern, and saves water by allowing you to control how much water is used in a flush.
Mr Wilkes said his original design replaced the whole siphon and flimsy diaphragm – but he had not been able to develop this design because it was too costly.
But the success of the Interflush meant Mr Wilkes had the resources to develop and produce his original design – the Saver Siphon, released this week.
He said the traditional toilet diaphragm was made of thin plastic sheeting which was more prone to tearing.
He said: "The Saver Siphon does exactly the same as the Interflush but the diaphragm is made from solid plastic so it should never fail.
"Once you have one of these fitted it should last forever.
"It turns a nine litre toilet into a 4.5 litre toilet."
Mr Wilkes won a Reporter Series Business Award in 2009 for his invention.
The Saver Siphon is available for 19.90 from Varyflush on 01924 500510.