Transient simulations of two phase gas-liquid flow in pipes require considerable computational efforts. Available commercial Codes that were developed, or are being developed at the present, use either the two fluid model or the drift flux model. These models implement continuity and momentum transient equations. In many occasions, in particular for the oil and gas industry, the transient response is usually relatively slow. Thus, it is suggested here to use quasi equilibrium momentum equations for the liquid and the gas together with transient continuity equations. This procedure results in a simplified numerical algorithm which can be used as an efficient transient simulator.