Tempering Valve for Hot Water Systems: Complete Buyer’s Guide

Jun 29, 2026

A tempering valve is one of the most important safety and compliance parts used with many hot water systems. It blends hot water with cold water to help deliver safer controlled temperatures to bathrooms and other sanitary fixtures. If you are replacing a hot water system, the tempering valve may also need to be checked, replaced or upgraded. At Hot Water Outlet, you can compare supply-only hot water systems and compatible valves, pipework and fittings, including options for electric hot water systems, heat pump hot water systems, gas hot water systems and instant gas hot water systems.

Quick Answer

A tempering valve mixes hot and cold water to reduce the delivered hot water temperature to safer levels at fixtures such as showers, baths and basins.

You may need a tempering valve when installing or replacing:

Electric storage hot water systems
Heat pump hot water systems
Gas storage hot water systems
Solar hot water systems
Some instant gas hot water systems, depending on setup
Hot water systems supplying bathrooms or sanitary fixtures

The exact requirements depend on the system type, temperature setting, outlet use, existing plumbing and local compliance requirements.

A licensed plumber should confirm whether a tempering valve is required and what type is suitable.

Supply-only pricing for a hot water system usually does not include tempering valves, installation, plumbing labour, fittings, pipework changes, drainage work, old unit removal, disposal or compliance upgrades unless specifically shown at checkout.

What Is a Tempering Valve?

A tempering valve is a plumbing valve that blends hot water from the hot water system with cold water from the mains supply.

Its purpose is to reduce the delivered water temperature to a safer controlled temperature before it reaches selected outlets.

For example, a storage hot water system may store water at a higher temperature, while the tempering valve helps reduce the water delivered to bathrooms.

A tempering valve is commonly installed near the hot water system or in the pipework serving the relevant fixtures.

Why Tempering Valves Matter

Tempering valves matter because hot water can cause burns if delivered at unsafe temperatures.

They also help with:

Safer bathroom water temperatures
Compliance requirements
Hot water system replacement work
Temperature control to sanitary fixtures
Managing stored hot water systems
Protecting users such as children, elderly people and guests
Reducing scalding risk
Separating bathroom temperature from hotter kitchen or laundry water where designed that way

A tempering valve is not just an optional extra in many installations. It may be required depending on the setup.

Tempering Valve vs Thermostatic Mixing Valve

Tempering valves and thermostatic mixing valves both mix hot and cold water, but they are not always the same thing.

Valve Type	Common Use	Main Purpose
Tempering valve	Domestic hot water systems	Helps reduce hot water delivery temperature to safer levels
Thermostatic mixing valve	Higher control applications, healthcare, childcare, commercial or special-use sites	Provides tighter temperature control where required
Standard mixer tap	User-controlled tap mixing	Mixes hot and cold at the tap, but does not replace required system temperature control

A standard mixer tap is not the same as a tempering valve. If a tempering valve is required, a normal tap mixer does not remove that requirement.

When Do You Need a Tempering Valve?

A tempering valve may be needed when a hot water system supplies bathrooms, showers, baths or other sanitary fixtures.

It is commonly associated with:

Electric hot water systems
Heat pump hot water systems
Gas hot water systems
Solar hot water systems
Storage hot water tanks
Replacement hot water systems
Homes with children or elderly occupants
Rental properties
Apartments and townhouses
Renovations and bathroom upgrades

The exact requirements should be confirmed by a licensed plumber.

Hot Water Systems That Commonly Use Tempering Valves

Electric Storage Hot Water Systems

Electric hot water systems commonly store hot water in a tank.

A tempering valve may be needed because the water stored in the tank can be hotter than the temperature allowed or recommended at bathroom outlets.

Electric Storage Buyer Checks

Check:

Existing tank temperature
Whether bathrooms are supplied
Existing tempering valve age
Existing valve condition
Water pressure
Tank size
Indoor or outdoor location
Pipework layout
Whether the replacement system changes connection points

If replacing an electric storage tank, do not assume the old tempering valve should automatically be reused.

Heat Pump Hot Water Systems

Heat pump hot water systems also store hot water, so they often need similar temperature control checks to electric storage systems.

A tempering valve may be required depending on the system setup and fixtures supplied.

Heat Pump Buyer Checks

Check:

Storage temperature
Hot water delivery temperature
Existing valve setup
Heat pump model requirements
Pipework layout
Water pressure
Drainage
Whether the valve is accessible
Whether the existing valve is suitable for the replacement

Heat pumps also need airflow, condensate drainage, electrical supply and noise placement checks. The tempering valve is only one part of the full setup.

Gas Storage Hot Water Systems

Gas hot water systems that store hot water may also need a tempering valve where bathrooms or sanitary fixtures are supplied.

Gas Storage Buyer Checks

Check:

Natural gas or LPG
Tank temperature
Bathroom outlet temperature
Existing valve condition
Water pressure
Gas storage model
Pipework setup
Drainage and relief valve discharge

Natural gas and LPG are not interchangeable. Gas fitting work must be completed by a licensed gas fitter.

Solar Hot Water Systems

Solar hot water systems can reach high water temperatures, especially during strong sun conditions.

A tempering valve is commonly important for solar hot water setups because stored solar-heated water can vary in temperature.

Solar Buyer Checks

Check:

Electric boosted or gas boosted setup
Roof-mounted or split solar system
Storage temperature variation
Existing valve age
Whether the valve is suitable for solar conditions
Whether the system is being replaced with heat pump, electric or gas
Whether solar pipework is being altered

Replacing solar hot water may involve extra work such as solar pipework isolation, roof collector removal, booster changes or drainage alterations.

Instant Gas Hot Water Systems

Instant gas hot water systems may or may not need a separate tempering valve depending on the appliance type, temperature setting, controller setup and outlets supplied.

Some instant gas systems are factory temperature limited. Others may be set at higher temperatures or supply mixed outlet types.

Instant Gas Buyer Checks

Check:

Natural gas or LPG
Appliance maximum temperature
Controller setup
Bathroom outlet requirements
Kitchen and laundry outlet requirements
Whether a tempering valve already exists
Whether the unit is temperature limited
Licensed plumber and gas fitter confirmation

External gas hot water units are outdoor/external only unless the product is specifically designed and approved for internal or flued installation.

Where Is a Tempering Valve Installed?

A tempering valve is usually installed in the pipework near the hot water system or on the hot water line serving selected fixtures.

The exact location depends on:

System type
Pipework layout
Whether all outlets or only bathrooms are tempered
Access for future servicing
Cold water supply location
Hot water outlet location
Existing valve setup
Available space
Compliance requirements

A licensed plumber should choose the correct location.

What Temperature Does a Tempering Valve Deliver?

A tempering valve is used to reduce delivered hot water temperature to safer levels for selected fixtures.

The exact delivery temperature depends on the valve, adjustment, system design and compliance requirements.

A licensed plumber should set and test the valve correctly.

Do not adjust a tempering valve yourself. Incorrect adjustment can create unsafe hot water temperatures, poor performance or compliance issues.

Signs a Tempering Valve May Be Faulty

A tempering valve can wear, block, fail or become inaccurate over time.

Common signs may include:

Hot water is too hot at bathroom outlets
Hot water is too cold
Temperature fluctuates
Shower temperature changes suddenly
Poor hot water flow
Water only gets lukewarm
Valve is leaking
Valve is corroded
Valve is old or seized
Hot water takes longer than normal to stabilise

These symptoms can also be caused by other issues, such as the hot water system, water pressure, blocked strainers, pipework, mixer taps or gas supply problems.

A licensed plumber should diagnose the cause before parts are replaced.

Can an Old Tempering Valve Be Reused?

Sometimes, but it depends on condition, age, compliance and suitability.

An old tempering valve may not be suitable if it is:

Leaking
Corroded
Seized
Blocked
Not controlling temperature correctly
Not accessible
Not compatible with the new system
Past reasonable service life
Installed incorrectly
Not compliant with the replacement setup

When replacing a hot water system, the tempering valve should be checked as part of the overall valve and fitting setup.

Do All Hot Water Systems Come With a Tempering Valve?

No. Do not assume a tempering valve is included with the hot water system.

Some product listings may include selected accessories, while others are supply-only for the unit itself.

Before ordering, check:

Product inclusions
Whether valves are included
Whether a valve kit is separate
Whether fittings are included
Whether installation parts are separate
Whether your plumber is supplying parts
Whether valves, pipework and fittings need to be ordered separately

Supply-only pricing usually does not include the full valve kit or installation materials unless clearly stated.

Tempering Valve vs Pressure Limiting Valve

A tempering valve and a pressure limiting valve do different jobs.

Part	Main Job
Tempering valve	Mixes hot and cold water to control outlet temperature
Pressure limiting valve	Reduces incoming water pressure
Duo valve	Provides isolation and non-return function in some setups
Expansion control valve	Helps manage expansion pressure on storage systems
Relief valve	Discharges water when pressure or temperature relief is required

A pressure limiting valve does not control temperature. A tempering valve does not reduce mains pressure. Many systems may need more than one type of valve.

Tempering Valve and Water Pressure

Water pressure can affect hot water performance and valve operation.

If pressure is too high, too low or unbalanced, the system may have temperature or flow issues.

Pressure-related checks may include:

Incoming mains pressure
Pressure limiting valve condition
Cold water supply pressure
Hot water pressure
Valve rating
Pipe sizing
Mixer tap performance
Flow restrictions

If the hot water temperature is unstable, the issue may not be the tempering valve alone.

Tempering Valve and Hot Water Flow

A faulty, blocked or incorrectly selected tempering valve can affect hot water flow.

Possible symptoms include:

Low hot water flow
Reduced shower pressure
Lukewarm water
Inconsistent temperature
Poor flow to bathrooms only
Better hot water at kitchen than bathroom
Temperature changing when other taps are used

A licensed plumber should check whether the valve, pipework, water pressure, hot water system or fixture is causing the problem.

Tempering Valve for Rental Properties

Rental properties should be checked carefully because hot water complaints can become urgent and safety-related.

For rentals, check:

Existing valve condition
Delivered bathroom temperature
Tenant complaints about hot or cold water
Hot water system age
Valve accessibility
Whether the hot water system is being replaced
Whether the valve is leaking or seized
Compliance requirements
Licensed plumber documentation

A cheap hot water replacement can become a problem if the old tempering valve is reused when it should have been replaced.

Tempering Valve for Apartments and Townhouses

Apartments and townhouses can have tighter access and more complex plumbing layouts.

Check:

Existing system location
Cupboard space
Safe tray setup
Valve access
Body corporate rules
Drainage
Water pressure
Whether the valve is inside a cupboard or service area
Whether the system supplies only one unit
Whether shared services are involved

A tempering valve should be accessible for future servicing. If it is hidden behind walls, cupboards or inaccessible pipework, replacement can become more difficult.

Tempering Valve for Heat Pumps

Heat pumps commonly store hot water at higher temperatures than what should be delivered directly to some fixtures.

When buying a heat pump, check:

Whether a tempering valve is required
Whether the old valve can be reused
Whether the valve suits the heat pump setup
Whether the pipework layout changes
Whether the system stores water at a different temperature
Whether the valve location remains accessible
Whether drainage and pressure control are also required

A heat pump replacement may also need condensate drainage, relief valve drainage, electrical work and suitable airflow.

Tempering Valve for Solar Hot Water

Solar hot water can produce very hot stored water, so temperature control is important.

When replacing or repairing solar hot water, check:

Existing tempering valve
Solar-compatible valve requirements
Existing storage temperature
Booster setup
Whether the system is being converted to heat pump, electric or gas
Whether roof collectors are staying
Whether pipework is being changed
Whether the old valve is accessible

Solar hot water replacement may involve more parts than a normal tank replacement.

Tempering Valve for Gas Hot Water

Gas storage systems may need a tempering valve when supplying bathrooms.

Instant gas systems depend on setup, appliance temperature, controllers and outlet requirements.

For gas hot water, check:

Natural gas or LPG
Storage or instant gas
Appliance maximum temperature
Bathroom outlet temperature
Controller settings
Existing valve condition
Whether kitchen and bathroom outlets are controlled differently
Licensed gas fitting requirements

Gas work must be completed by a licensed gas fitter.

Tempering Valve for Electric Hot Water

Electric storage systems commonly require temperature control where bathroom outlets are supplied.

When replacing electric storage, check:

Tank storage temperature
Existing tempering valve condition
Whether the valve is leaking or seized
Whether the new tank connection points change
Whether the old valve is accessible
Whether water pressure control is needed
Whether safe tray and drainage are required

A new electric tank does not automatically mean the old valve setup is acceptable.

Buying a Tempering Valve Online

Before buying a tempering valve online, check:

System type
Pipe size
Connection size
Temperature range
Valve rating
Brand and model
Water pressure requirements
Whether it suits the application
Whether it is for domestic or commercial use
Whether additional fittings are needed
Whether a licensed plumber has confirmed suitability

The wrong valve may not fit, may not perform correctly or may not suit the system.

What Else Might You Need With a Tempering Valve?

A tempering valve may not be the only part required.

Depending on the installation, you may also need:

Pressure limiting valve
Duo valve
Expansion control valve
Isolation valves
Non-return valve
Relief drain materials
Connection fittings
Pipework materials
Safe tray parts
Heat pump condensate drainage parts
Gas isolation valve if gas is involved

You can compare compatible valves, pipework and fittings online.

Common Mistakes With Tempering Valves

Assuming the Old Valve Is Fine

An old valve may be seized, leaking, blocked or not controlling temperature correctly.

Confusing Pressure and Temperature

A pressure limiting valve controls pressure. A tempering valve controls temperature.

Buying the Wrong Valve

The valve must suit the system, pressure, pipe size and application.

Ignoring Flow Problems

Poor hot water flow may be caused by the tempering valve, but it may also be caused by pipework, water pressure, filters, strainers or fixtures.

Adjusting the Valve Yourself

Tempering valves should be installed, set and checked by a licensed plumber.

Forgetting About Compliance

Temperature control requirements can apply during replacement work.

Comparing Supply-Only Price to Installed Cost

Supply-only product pricing usually does not include valves, fittings, pipework, labour or compliance upgrades.

Assuming All Systems Need the Same Setup

Electric storage, heat pump, gas storage, instant gas and solar systems can have different valve requirements.

Buyer Checklist Before Ordering a Tempering Valve

Before ordering, confirm:

Hot water system type
Storage or instant system
Electric, gas, heat pump or solar setup
Natural gas or LPG if applicable
Whether bathrooms are supplied
Pipe size
Connection size
Water pressure
Existing valve condition
Existing valve location
Whether the valve is accessible
Whether a pressure limiting valve is also needed
Whether a valve kit is required
Whether drainage or pipework changes are needed
Whether the hot water system is being replaced
Licensed plumber requirements

Supply-Only vs Installed Cost

Hot Water Outlet sells supply-only hot water systems, valves and accessories online. Supply-only pricing is useful for comparing product costs, but it is not the same as total installed cost.

The final installed cost may depend on:

Licensed plumbing labour
Valve installation
Pipework changes
Access
Existing valve removal
Water pressure issues
Drainage work
Additional fittings
Hot water system replacement
Electrical work if the system is being replaced
Gas fitting if gas is involved
Compliance upgrades

Where appropriate, Hot Water Outlet may help organise quotes from reputable installers.

FAQ: Tempering Valves for Hot Water Systems

What does a tempering valve do?

A tempering valve mixes hot water with cold water to reduce the delivered hot water temperature to safer levels at selected outlets, such as showers, baths and basins.

Do I need a tempering valve on my hot water system?

You may need a tempering valve depending on the system type, storage temperature, outlets supplied and compliance requirements. A licensed plumber should confirm what applies.

Do electric hot water systems need tempering valves?

Many electric storage systems require temperature control where bathrooms or sanitary fixtures are supplied. A licensed plumber should confirm the correct setup.

Do heat pump hot water systems need tempering valves?

Heat pumps often store hot water and may require a tempering valve depending on the system and outlets supplied.

Do instant gas systems need tempering valves?

Some instant gas systems may not need a separate tempering valve if they are temperature limited, while other setups may require one. It depends on the appliance, settings, controllers and outlets.

Can I reuse my old tempering valve?

Sometimes, but only if it is suitable, compliant and in good condition. Old valves may be leaking, seized, blocked or inaccurate.

How do I know if my tempering valve is faulty?

Signs may include water that is too hot, water that is too cold, fluctuating temperature, poor flow, leaking, corrosion or inconsistent shower temperature.

Can I adjust a tempering valve myself?

No. A tempering valve should be installed, adjusted and checked by a licensed plumber.

Is a tempering valve included with a hot water system?

Not always. Many supply-only hot water systems do not include a tempering valve or full valve kit unless specifically listed.

Does supply-only pricing include tempering valve installation?

No. Supply-only pricing generally does not include installation, plumbing labour, pipework changes, fittings or compliance upgrades.

Can Hot Water Outlet install a tempering valve?

Hot Water Outlet sells supply-only hot water systems, valves and accessories online. Plumbing work must be completed by appropriately licensed tradespeople. Where appropriate, Hot Water Outlet may help organise quotes from reputable installers.

Final Thoughts

A tempering valve is a key part of many hot water systems because it helps control delivered water temperature. When replacing a hot water system, the tempering valve should be checked along with the pressure limiting valve, isolation valves, drainage, pipework and other fittings.

Do not assume the old valve is suitable, and do not compare supply-only hot water system pricing to a complete installed job.

Browse valves, pipework and fittings, compare hot water systems, electric hot water systems, heat pump hot water systems, gas hot water systems and instant gas hot water systems online at Hot Water Outlet.

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