The powerful prop suffered a neck injury ten months ago and has never been able to regain his place since Duncan Bell, the former Ebbw Vale player, was signed from Sale.
Tau has joined Division One club Pontypool, who already have a Tongan prop in Uniata Moa, and will be eligible to play in the seventh round Principality Cup tie against Swansea at Pontypool Park on Friday, February 22.
With Moa competing for the loose-head job, Tau will play on the tight-head of the front row and the 33-years-old, with almost as many caps as his age, at 18 stones seven pounds will give the Pontypool chances a huge boost.