The still variant's label has black text on a white background, while the sparkling version sports the reverse. Both are available in 330ml and 750ml sizes with a tamper-proof seal more common to wine bottles.
The company has already secured listings for the brand, which is sourced from the Welsh Cambrian Mountains in Harrods and Selfridges. David Relph, Ty Nant sale and marketing manager, said most clear bottles were too old-fashioned to fit the contemporary style of some outlets.
The name Tau comes from a Welsh word meaning to be silent'.