Hi Ria,What has worked ...

Hi Ria, What has worked effectively for me is to have a small trace of Free Chlorine in the feed water (typically 0.2 - 0.5 mg/L Free Chlorine). Then periodically slug dose a larger concentration (5-10ppm). Slug dose should be irregular, to prevent organisms acclimatising to the daily rhythm. I've reviewed pipework after 24 months and 5 years and had no barnacle growth observed using this regime. This can be done using either liquid hypochlorite (Sodium), or by using electrochlorination (cheaper but has drawbacks). The free chlorine should be applied as close as possible to the intake structure (growth will occur from the point of intake). Hope this helps. Anthony