Scalds and hot water temperatures

Cold first, then hot, and stir. Test with your elbow before anyone gets in, as RoSPA advises for children.⁵ Hot bath water causes the most fatal and severe scalds among young children, and children can drown in very small amounts of water, so no young child is left alone in the bath, even for a moment.⁵ See young children for the wider picture.

This is the lasting fix, and it sits on the pipework, out of the bather's reach. A competent plumber fits it, sets the temperature limit, and tests it. Approved Document G names valves shown to meet BS EN 1111 or BS EN 1287, which should fail safe and should not be easily altered by the people who use the room.¹ In England a new bathroom in an existing home does not need one by law, though the potential safety benefits are worth weighing.² Ask the plumber which standard the valve meets.

A thermostatic shower holds the temperature you set when the supply changes. Whether it also limits the hottest setting, and fails safe if the cold supply drops, depends on the valve inside, so ask. Test the first water on your hand, not your head, and keep the dial away from the hottest end for children and older people. For anyone who cannot get out of the way of hot water quickly, the outlet limit matters more than the dial. See thermostatic mixing valves.

Because stored hot water is kept hot to keep bacteria such as legionella in check. HSE's guidance for health settings puts hot stored water above 60°C.⁴ A cylinder set cooler to protect a bather leaves the water in it at risk. The way to limit scalds is a valve at the outlet, fitted by a competent plumber, with the stored water left alone. In a rented home, HSE landlord guidance says tenants are told not to adjust it; if you rent, ask the landlord.⁷