What Is TVC?
Total Viable Count (TVC) refers to the total number of live microorganisms present in a water sample. It is commonly used as an indicator of general water quality in potable drinking water systems.
TVC does not identify specific bacteria or pathogens. Instead, it provides an overall measure of bacterial activity, which can be influenced by factors such as temperature, stagnation, system design, and water usage.
TVC levels cannot be assessed by appearance, taste, or smell. Laboratory testing is required to determine bacterial levels accurately.
Why is TVC testing important?
TVC testing provides insight into the general condition of a water system at the time samples are taken. Elevated results may indicate changes within the system that could support bacterial growth or reduced water quality.
TVC testing is commonly used in:
- Residential properties
- Commercial and public buildings
- Care and healthcare environments
- Low-use or intermittently occupied premises
- Anywhere with a potable cold water storage tank
TVC testing is not used to diagnose specific risks but can support broader water monitoring and management processes.
How TVC testing works
Water samples are collected from selected outlets and potable cold water storage tanks then analysed by an independent laboratory. Results are issued in a formal report showing the level of bacterial growth identified at the time of testing.
This service provides laboratory testing and reporting only. Interpretation, risk assessment, and remedial advice should be considered separately where required.
When should TVC testing be taken?
TVC testing may be considered:
- As part of routine water quality monitoring
- Following periods of low or irregular water use
- After changes to a water system
- Where reassurance or baseline information is required
- Where a building has a cold water storage tank supplying potable (drinking) water, six-monthly TVC testing is a recognised requirement as part of routine water quality monitoring for that system.
The need and frequency of testing will depend on the specific water system and how it is used.
For information on specific waterborne bacteria, including Legionella, see our Legionella testing guide.