The following applies to any version of the biosand filter that is being used.
Proper installation includes a high quality filter body, lid, diffuser, safe storage container and well prepared filtration sand. Our recommendation for preparing the filtration sand is to use 0.7 mm (0.028") opening size screen, also called #24 wire mesh. The detailed instructions for construction, installation and operation are in CAWST's biosand filter manual.
If a filter is not installed properly or is not being operated properly, then we can expect that the filter is not working properly. It may not produce good water consistently.
The following eight operating conditions must be met for the Version 10 biosand filter to work properly and consistently:
- Filter is used for at least one month since installation
- Filter is used at least once each day
- Source water is not too turbid (less than 50 NTU)
- The concrete filter body is not leaking
- Diffuser is in place and in good condition
- Water level is 5 cm above the sand during the pause period
- Top of sand is level
- Flow rate is 0.4 litres per minute or slower (Note: The flow rate for Version 8 or Version 9 is 0.6 litres per minute or slower)
CAWST recommends checking these eight operating conditions and fixing any identified problems to ensure the best results.
