Source-backed values from Approved Document G for new dwellings and fixed baths.
Approved Document G is useful for source-backed value recall because it gives separate anchors for water efficiency and for hot-water safety — two different aims that learners often blur together.
Water efficiency. For a new dwelling the normal limit is 125 litres per person per day, worked out with the water-efficiency methodology from the fittings specified — WCs, taps, showers, baths and any water softener or outdoor supply. Where the optional requirement is imposed through planning, the tighter figure is 110 litres per person per day, which usually means choosing lower-consumption fittings.
Hot-water safety at a bath. In a new dwelling in England, hot water supplied to a fixed bath is limited to a maximum of 48 °C. A suitable blending valve or other appropriate temperature-limiting device can provide that control. The cylinder’s hygiene regime remains a separate requirement. The 48 °C ceiling is not suitable for every bather: where vulnerable users are at risk during whole-body immersion, water must not exceed 44 °C and may need to be cooler.
Keep these as Building Regulations revision facts, and remember which is which: 125 or 110 litres is water efficiency, 48 °C is scald safety. They do not replace the full document, local building-control advice, manufacturer instructions or practical assessment requirements.
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