What Temperature Should Hot Water Be At The Tap?

The ideal hot water temperature isn't simply one number for every home.

There's an important difference between the temperature at which water is stored, the temperature it reaches through the pipework and the temperature that's safe to use at a tap, bath or shower.

Understanding that difference can help you keep your hot water system safe without setting temperatures unnecessarily high.

What temperature should hot water be at the tap?

For hot water systems using temperature to control Legionella, HSE guidance states that hot water should be stored at at least 60°C and distributed so that it reaches at least 50°C within one minute at outlets.

That doesn't mean every tap or shower should necessarily deliver water to the user at 50°C or above.

Where there is a significant risk of scalding, a thermostatic mixing valve (TMV) can blend hot and cold water close to the outlet to provide water at a safer temperature.

This distinction is important. The temperature required within the hot-water system and the safe temperature for bathing aren't necessarily the same.

Why is 60°C important for stored hot water?

Stored hot water requires particular attention because warm, stagnant water can provide conditions in which Legionella bacteria multiply.

Where temperature is being used as the control method, hot water cylinders should generally store water at 60°C or above. The hot water should then be distributed at a sufficient temperature to reach at least 50°C within one minute at the relevant outlets.

This is particularly relevant to homes and buildings with a hot water cylinder, where water is stored before use.

Turning the cylinder temperature down significantly in an attempt to save energy isn't recommended without understanding how the system is designed to manage Legionella risk.

Is 50°C too hot for a tap?

Water at 50°C can still present a scalding risk, particularly with prolonged exposure or for people who are more vulnerable to burns.

This is why simply aiming for the highest possible tap temperature isn't the answer.

Where scalding is a significant concern, TMVs can be fitted close to baths, showers or other outlets. These automatically mix hot and cold water to limit the temperature delivered to the user while allowing the wider hot-water system to operate at the temperatures required for effective temperature control.

Children, older people and people with reduced mobility or sensitivity can be particularly vulnerable to scalding.

What temperature should a hot water cylinder be set to?

If your home uses a hot water cylinder, 60°C is the key temperature to remember.

Keeping stored hot water at this temperature helps control the risk of Legionella bacteria multiplying within the system.

The water doesn't necessarily have to reach you at 60°C. Depending on the installation, pipework and any TMVs fitted, its temperature can be reduced before it reaches the point of use.

The cylinder setting and tap temperature therefore shouldn't be treated as the same measurement.

What about hot water from a combi boiler?

A combi boiler works differently because it heats domestic water on demand rather than keeping a large cylinder of hot water ready for use.

When you open a hot tap, cold mains water passes through the boiler and is heated before being sent to the outlet.

Many modern combi boilers allow you to adjust the domestic hot-water temperature from the boiler controls. The exact setting and adjustment process varies by manufacturer and model, so check the instructions supplied with your boiler rather than assuming every appliance should be adjusted in the same way.

If your hot water is unexpectedly cold rather than simply set to the wrong temperature, that may indicate a separate boiler or plumbing issue.

How do you check the temperature of hot water at the tap?

If you want to check how hot your water actually is, use a suitable thermometer rather than judging it by touch.

Run the hot tap and allow the temperature to stabilise before taking a reading. Remember that the temperature at the outlet can differ from the setting shown on your boiler or cylinder controls because heat can be lost as water travels through the pipework.

If your system has a TMV, the temperature at that particular outlet may also be deliberately limited.

How do you adjust your hot water temperature?

How you adjust the temperature depends on the type of heating and hot-water system you have.

Combi boiler

Modern combi boilers commonly have separate controls for central heating and domestic hot water. Look for the hot-water control on the boiler display or control panel and make small adjustments as required.

The exact controls vary between models, so check your manufacturer's instructions if you're unsure which setting controls domestic hot water.

For a more detailed walkthrough, see iHeat's guide to adjusting the water temperature on your boiler.

Hot water cylinder

If you have a system or heat-only boiler with a hot water cylinder, the stored-water temperature is normally controlled by the cylinder thermostat.

Stored hot water should generally be maintained at 60°C or above where temperature is being used to control Legionella.

Don't simply turn the cylinder thermostat down because the water at your bath or shower feels too hot. If scalding is a concern, the safer solution may involve controlling the temperature closer to the outlet.

What does a thermostatic mixing valve do?

A thermostatic mixing valve, or TMV, blends hot and cold water to control the temperature supplied at an outlet.

This allows stored hot water to remain at the temperature required for effective Legionella control while reducing the risk of excessively hot water reaching the person using a bath, shower or other outlet.

TMVs can be particularly important where people are more vulnerable to scalding.

If you have a TMV and the water suddenly becomes much hotter or colder than normal, the valve may need to be checked rather than simply changing the boiler or cylinder temperature.

Why is my hot water not reaching the right temperature?

If your hot water used to reach a suitable temperature but has suddenly become much hotter or colder, don't assume the temperature setting is necessarily responsible.

The cause can depend on your system and which outlets are affected.

If every hot tap is cooler than expected, check the temperature setting and whether your boiler or hot-water system is operating normally.

If only your shower stays cold while other hot taps work correctly, the issue may be specific to the shower rather than the boiler. See iHeat's guide to why your shower is cold and not getting hot.

If the water repeatedly changes between hot and cold, that's a different symptom again and should be investigated separately.

Should you turn your hot water temperature down to save energy?

Heating water to a higher temperature than necessary can waste energy, but the safe approach depends on your hot-water system.

With a combi boiler, which heats domestic water on demand, the hot-water setting can usually be adjusted independently from the central-heating flow temperature.

Stored-water systems require different consideration because temperature is also used to help control Legionella. You shouldn't reduce a hot water cylinder below recommended storage temperatures simply to reduce energy consumption.

Understanding whether your home has a combi boiler or stored hot-water system is therefore important before changing any settings.

Hot water temperature FAQs

What temperature should hot water be at the tap in the UK?

Where temperature is used to control Legionella, hot water should generally reach at least 50°C within one minute at outlets. However, the temperature delivered to the user may be reduced locally using a TMV where there is a significant scalding risk.

What temperature should stored hot water be?

Hot water should generally be stored at 60°C or above where temperature is being used as the method of controlling Legionella.

This is different from the temperature that may ultimately be delivered at a bath, shower or other outlet.

Is 60°C too hot for tap water?

Water at 60°C presents a significant scalding risk and shouldn't be treated as a universally appropriate temperature at the point of use.

For stored-water systems, 60°C is important for controlling Legionella within the system. Where necessary, a TMV can then reduce the temperature before the water reaches the user.

Is 50°C hot enough for domestic hot water?

It depends on what you're measuring.

HSE guidance states that hot water should reach at least 50°C within one minute at outlets where temperature is being used for Legionella control. Stored hot water should generally be kept at 60°C or above.

A lower temperature may be deliberately provided after a TMV at an outlet where scalding risk needs to be controlled.

What temperature should a combi boiler be set to for hot water?

Combi boilers heat domestic water on demand rather than storing a cylinder of hot water, so their requirements differ from stored systems.

The appropriate setting depends on the boiler, your requirements and the manufacturer's instructions. Many modern combis allow the domestic hot-water temperature to be adjusted separately from the central-heating temperature.

Why is my hot water suddenly hotter than normal?

First check whether the temperature setting has been changed. If it hasn't, an unexpectedly high outlet temperature could require further investigation.

Where a TMV is fitted, a problem with the valve can also affect the temperature delivered at the outlet.

If you're unable to identify the cause safely from the user controls, have the system checked by a suitably qualified professional.

Why is my hot water only lukewarm?

Check whether the problem affects every hot-water outlet or only one.

If all of your hot taps are cooler than normal, check the temperature setting and whether your boiler or hot-water system is operating correctly. If only one shower or tap is affected, the problem may be local to that outlet.

Getting your hot water temperature right

The right hot-water temperature depends on where in the system you're measuring it.

For stored systems, keeping hot water at 60°C or above is important where temperature is used to control Legionella. Hot water should generally reach at least 50°C within one minute at outlets, while TMVs can provide additional protection against scalding where required.

Combi boilers work differently because they heat domestic water on demand, so always distinguish between combi hot-water settings and stored-cylinder temperatures before making adjustments.

If your water has suddenly become much hotter, colder or less consistent without you changing the settings, the underlying problem may need investigating rather than simply turning the temperature up or down.