If there is an immediate colour change (within 20-30 minutes before incubation) in either the Biofilm or Bacteria Test Vial, do not proceed with testing as results will be inaccurate. Immediate colour change indicates your water source is out of range for testing. Your water pH can be too high or too low due to many factors such as your current disinfectant. A highly acidic disinfectant such as peracidic acid or a highly alkaline disinfectant such as bleach can change your water pH. We recommend contacting your water provider for more details.