Quote: "
Under the Workplace (Health, Safety and Welfare) Regulations (Northern Ireland) 1993, a supply of potable drinking water must be made available to all employees of a business. However as health and safety legislation is very much geared towards the employer / employee relationship, it does not extend to customers.
Not sure that there would be any statutory duty on the airport to provide free potable water, but simply more a customer service issue."
AFAIK, and correct me if this wrong, there is a "duty of care" in health and safety legislation. Employers have a "duty of care" to employees and customers/visitors and employees have a "duty of care" to each other and also to customers/visitors.
Whether or not this includes a supply of drinking water, who knows, but as you say it's a general customer service issue.