Safe hot water temperature: why 50°C in the bathroom matters

Hot water burns are among the most common serious burns in Australian homes, and most happen in the bathroom. The fix is simple: hot water to the bath, shower and basin should be no hotter than 50°C. This guide explains why, what the NSW rules say, how to check your own water, and what to do if it's running too hot. It's written by the licensed plumbers who install and service hot water systems across the southern Eastern Suburbs.

Two temperatures, two jobs

A tempering valve, fitted on the hot water line, does the cooling. It blends in just enough cold water to bring bathroom water down to 50°C. The kitchen and laundry are usually left on the hotter supply. See our tempering valve page.

How quickly hot water burns

The hotter the water, the faster it burns. At 60°C, water can cause a serious burn to an adult in about a second. At 50°C, it takes several minutes, which gives people time to react and get out of the way. Young children have thinner skin and burn much faster than adults, and older people may react more slowly or have less feeling in their hands and feet. For them, those extra degrees make all the difference.

What the rules say in NSW

Under the plumbing rules NSW follows, bathroom hot water outlets must deliver water at no more than 50°C when a hot water heater is installed or replaced. A temperature control device, usually a tempering valve, has to be fitted to do that. It applies to like-for-like replacements too, not just new homes.

Homes whose hot water system went in before these rules may have no tempering valve at all. There's nothing stopping you adding one now, and if you have young children or older relatives in the house, it's well worth doing.

How to check your hot water temperature

• Run the bathroom hot tap for a minute or two until the temperature stops rising.
• Hold a kitchen or cooking thermometer in the stream, or fill a cup and test it straight away.
• If it reads well over 50°C, the bathroom may have no tempering valve, or the valve may have failed.
• Never test by hand. If you're unsure, ask a plumber to check it.

Don't try to adjust a tempering valve or the thermostat on a hot water system yourself. Settings are made and tested by a licensed plumber to keep both the stored water and the bathroom water at the right temperatures.

Everyday ways to prevent scalds

• When running a bath, turn the cold tap on first and off last.
• Test bath water with your elbow before a child gets in, and never leave young children alone in the bath.
• Keep children away from the taps while the bath is filling.
• If an older family member lives with you, ask a plumber to check the bathroom temperature.

Hot water in southern Eastern Suburbs homes

We still find plenty of older homes in Matraville, Maroubra, Malabar and Botany where the shower runs at full storage temperature because the hot water system pre-dates tempering valves. We also see valves that were fitted years ago and have since worn out, so the temperature creeps up without anyone noticing. A quick test is the easiest way to know.

Related help: tempering valves, hot water repairs and replacement, our hot water guide and TMV testing. Local pages: hot water Matraville, hot water Maroubra, hot water Coogee and hot water Kingsford. Browse all our plumbing guides.