This paper reports experimental assays on the utilisation of the ozone technology to disinfect backyard swimming pool waters. Tests were carried out utilizing a semi-batch reactor in which various samples containing 10 3 CFU/mL of E. coli, E. hirae, S. aureus and P. aeruginosa were treated considering different dissolved ozone doses. Results show a low disinfection activity at ozone concentration of 0, 05 mgO 3 /L, a potential to disinfect water in 5-15 seconds at concentration around 0, 10 mgO 3 /L and a drastic abatement of the disinfection capabilities under the concentration of 0, 01 mgO 3 /L. Some ozone purging and microorganisms revitalization trials were carried out too.