How to fit and commission thermal balancing valves: A best practice guide


Thermal Balancing Valves (TBVs) have an important role to play in the commissioning of any commercial hot water system. As well as ensuring that the system operates effectively and provides energy efficiency benefits, they are critical to maintaining the health and safety of the system and its users. Failing to fit a TBV can overwork the boiler, cause hot water to fail and even be the cause of a Legionella outbreak.

We share our top tips for safe commissioning and installation of TBVs.

What are thermal balancing valves?

TBVs are designed to balance the hot water and maintain the temperature throughout the circuit. They achieve this by dynamically adjusting the flow rate of hot water – maintaining the temperature in the circuit by forcing hot water to other parts of the system that have a lower temperature.

At RWC, we have developed a range of innovative and efficient Thermal Balancing Valves from our Reliance Valves brand. These valves are designed to reduce the flow of hot water from the boiler as the system temperature increases. However, if the temperature reaches 70°C, a bypass port is opened within the valve to allow an increased flow rate throughout the circuit to disinfect the system.

Hot Water TBV

Why are TBVs important?

TBVs are used to accelerate hot water delivery to the tap, reduce water wastage and conserve energy, as well as improving system efficiency and offering health and safety advantages.

Benefits include:

  • Preventing stagnation and combating Legionella: The TBV provides thermal balance in hot water systems to keep a constant water temperature (generally above 50°C.) This provides thermal disinfection against Legionnaires’, with the constant flow of water in the system reducing the likelihood of stagnation.
  • Access to immediate hot water: TBVs are designed to ensure immediate access to hot water when the tap is turned on. As well as offering added convenience, this feature reduces water wastage by avoiding the need to run the tap first.
  • Reduced ongoing maintenance: Maintaining a constant temperature within the system means less stress on the boiler and less likelihood of component damage, which can be caused by hot-spikes.

Top tips for fitting TBVs

As with anything that connects to a hot water system, correct installation is key to success and system efficiency. It’s worth noting that not following the supplier’s installation guidelines also invalidates the WRAS certification on your TBV.

  • Location, location, location: Thermal balancing valves should be installed on returning legs of the pipework to avoid creation of dead legs of uncirculated hot water. Placing TBVs on the return pipework that is closest to the boiler can result in a non-balanced circuit, as water does not get forced to areas of the system that is at a lower temperature. Instead, it means the boiler has to work harder to spike water temperatures to get hot water to areas that are furthest away.
  • Think big: In commercial applications, one TBV won’t do the job. Individual valves should be installed at every hot water draw-off area, ensuring a constant temperature across the circuit no matter where you are in the building.
  • A two-pronged approach to health and safety: TBVs can successfully eliminate temperature spikes and balance the hot water in the system. However, for protection against scalding and Legionnaires’, a Thermostatic Mixing valve should also be installed.
Plumber conducting TBV Inspection

Commissioning a TBV – things to think about

  • TBVs should be WRAS approved: WRAS approval is an easy way to demonstrate that a product is of suitable quality and standard and that it complies with the Water Supply (Water Fittings) Regulations or Scottish Byelaws, provided the fitting is installed according to any conditions given with the approval.
  • TBVs should operate automatically: An integral part of the safety of any hot water system, it is crucial that TBVs operate automatically and without any operator intervention.
  • TBVs should have adjustable temperature settings from 40°C – 65°C: TBVs should give installers the ability to set the temperature when they install and maintain the system.
  • Include an integral disinfection function: As an important component in the fight against Legionella and waterborne diseases, TBVs must include an integral disinfection function.
  • Regular servicing and maintenance: Maintaining the system is an important part of ensuring efficient temperature control. The piston and thermostat assembly of TBVs can accumulate dust over time, which can impact the performance of the system.
  • Keep records: With the installation and maintenance of any hot water system, we would always recommend keeping records. As well as being useful for the customer, keeping records of dates and temperature settings – and getting customers to sign them off – can cover you in the event of an issue.

For assistance with fitting and installing TBVs, including their role in ensuring safe and efficient hot water systems, our technical teams are on hand to help. You can get in touch with us here.

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Eric Winter Headshot

Eric Winter

EMEA Director of Product Development [Valves]

About the author

I've had the privilege of being a part of the RWC family for an incredible 25 years.

I joined the company in a technical support role and steadily progressed to become the Technical Director. Throughout my tenure, I've spearheaded the introduction of market-leading products that have revolutionised the industry.

In addition to product innovation, I am a member of WG14 working group, as part of the TC 164 technical committee, which is responsible for revising European and British valve standards. This multifaceted experience has equipped me with a deep understanding of the industry, positioning me as a trusted expert in my field.