At certain times of the year most sites may be closed or have a reduced number of users. Legionella prefer low usage or stagnant water and can grow to dangerous levels which makes infrequently used showers a high risk.
The pipework and showers must be flushed weekly, the shower heads and hoses descaled and disinfected regularly.
Camping grounds tend to be more seasonal than caravan sites, if the site only opens for the summer months, then the hot and cold water services should be disinfected before being put back into service. Communal showers should be tested just prior to opening to the public.