Tritiated water can be standardized by internal gas proportional counting following its chemical reduction, by means of a tritium gas generator, to produce tritiated hydrogen. In this paper a new tritium gas generator is described in detail together with the method of measurement based on the internal gas counting. It has new and improved features and offers the advantage of being simpler and easier to operate than other tritium generators available. Thus, this tritium generator has the following new features: (i) it performs the water reduction at a lower temperature (450°C) than the other generators which need 600°C ; (ii) the reduction yield is always unitary. Also, it has a simple and compact construction by using the same components for water degassing and water reduction. Its simple disassembly and reassembly allow for easy maintenance