This study was performed to improve water demand estimation and analize correlation between generation of domestic sewage and domestic water use. To improve the prediction of water demand estimation, new water demand equation was developed. The results is as follows. $InQ_t = {eta}_0+{eta}_1InP_t+{eta}_2InY_t+{eta}_3InH_t+{varepsilon}_t$By using the statistical analysis of the "generation of domestic sewage" and "domestic water use", the regression equation between them is formed. The result is as follows. Generation of domestic sewage : 0.8487 $ imes$ Domestic water use + 684.57 ($R^2$= 0.972)>$R^2$</TEX>= 0.972)