"There's no legal requirement to provide drinking water for staff..."
Drinking water
22.—(1) An adequate supply of wholesome drinking water shall be provided for all persons at work in the workplace.
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"Think about it. How would millions of people who work outdoors get such a thing?"
Application of these Regulations
3.—(1) These Regulations apply to every workplace but shall not apply to—
... [exemptions listed (a) to (d)]
...
...
(4) As respects any workplace which is in fields, woods or other land forming part of an agricultural or forestry undertaking but which is not inside a building and is situated away from the undertaking's main buildings—
...
(b) any requirement to ensure that any such workplace complies with any of regulations 20 to 22 shall have effect as a requirement to so ensure so far as is reasonably practicable.
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"Nor do they necessarily have to provide hand washing facilities..."
Washing facilities
21.—(1) Suitable and sufficient washing facilities, including showers if required by the nature of the work or for health reasons, shall be provided at readily accessible places.