Premise plumbing have special working conditions such as long-term detention of hydraulic regimes and intermittent water use. In this study, based on the hourly water consumption data of 1 100 households in a residential area of HZ City, an indoor non-circulating pipeline simulation platform was built, and five hydraulic regimes were set up: high varied flow (HIG), medium varied flow (MED), low varied flow (LOW), steady state (SS) and 168 h retention (RET), to explore the influence of special hydraulic conditions of premise plumbing on the microbial communities and opportunistic pathogens. After three months of operation, 33 sets of biofilm and water samples were collected, and real time qPCR and 16S rRNA gene sequencing analysis were performed. In addition, the absolute abundance of Pseudomonas aeruginosain the samples was quantified. The microbial community and diversity were analyzed. The results showed that the total number of RET water-like bacteria was the largest, and the proportion of viable bacteria in the biofilm was the highest. Conditionally pathogenic bacteria in the water samples has higher number and abundance under intermittent hydro-working conditions. The total number of bacteria in HIG biofilms and the highest relative abundance of conditionally pathogenic bacteria was 78.38%. The quantitative results of Pseudomonas aeruginosawere 4 798.81/cm², which was 7.59 times that of RET biofilms. The RDA results showed that turbidity and pH were the main environmental factors for Pseudomonas and Pseudomonas aeruginosa respectively.