Tap water
What it really means
Water from the tap — free and safe to drink everywhere in the UK. Restaurants that serve alcohol must give free tap water if you ask. Saying "just tap water, please" is completely normal, not rude or cheap.
Context, tips & common mistakes
UK tap water is safe and good everywhere, and premises licensed to serve alcohol are legally required to provide free drinking water — so asking is never cheeky: "could we get a jug of tap water for the table?" is said at every level of restaurant, including the expensive ones, and staff will not blink. Specify 'tap' clearly, otherwise 'water' can arrive bottled and billed.
Beyond restaurants, cafés generally refill bottles on request, refill-station apps map free water points in cities, and airport rules allow an empty bottle through security to fill airside. Buying bottled water in Britain is a taste preference, never a safety measure — money the newcomer budget does not need to spend.