Abstract: A domestic carbonator for gasifying liquid in a container comprising a cap for the container having an injector passage closed by a one-way non-return valve in combination with a main body having pressure-reducing discs, an injector piston for initiating a gas flow, a pressure relief valve and a pressure gauge. The main body is provided with an opening for receiving a CO.sub.2 cylinder with a further piston for cutting off the gas supply under the effect of the back pressure from the container.