Over time, mixing valves will scale. The temperature and the hardness of the water are two of the factors that can speed up that process. There isn’t a specific way to predict the appropriate service intervals unless you have a service record at that site to work from. You have two valve technology choices to keep the ongoing scale buildup in check:

Thermostatic Mixing Valves: Simple and Reliable 

If you need a straightforward way to regulate water temperature, thermostatic mixing valves (TMVs) are a tried-and-true solution. They use a wax element and sliding cartridges to control temperature, with no wires, and no complicated setup. This makes them a great fit for residential and small commercial applications.

They are available in many different kit combinations and assemblies for a small lay length if space is limited. If the setpoint doesn’t need to change and remote access isn’t required, they are a great fit. 

Why Choose a Thermostatic Mixing Valve? 

• Easy installation - no electrical wiring needed
• Simple setup - Adjust the knob and verify with the gauge
• Ideal for set-it-and-forget-it temperature control 

What to Watch Out For? 

• Scale buildup - Regular maintenance is required to keep the scale at bay 
• No advanced features - Thermostatic valves don’t offer automated controls or self-cleaning functions. 

Pro Tip: Keep service records to track maintenance intervals to help predict the right service schedule. 

Digital Mixing Valves: Precision and Performance 

For retrofit and new commercial projects, a big advantage of digital is the ability to see into the past with data logging. There are cases where the mixed water temperature bogs down, and you can access the data logger to do some plumbing detective work. We have helped plumbers identify cross connections and sporadic DHW recirc pump performance just by having a timestamp of when the temperature sensors show a drop. A thermostatic valve wouldn’t be able to tell much of a story. 

Digital mixing doesn’t mean complicated. Out of the box, they plug in with a wall transformer. You answer a few quick questions on the screen and you are set up for a simple mixing operation. If you want to run a Legionella bacteria management program, that is an option, too. The vast majority of retrofit switches to digital mixing valves are in projects where the plumber is tired of rebuilding a big high/low thermostatic mixing station that is constantly scaling up. 

What Makes Digital Mixing Stand Out? 

• Automated self-cleaning - daily ball rotation helps prevent scale buildup
• User-friendly - no need for a laptop, everything is accessible at the valve
• Thermal disinfection scheduling - helps manage Legionella risks with calendar-based programs
• Building automation integration - compatible with MODBUS® and BACnet™ for seamless system control  

Choosing the Right Valve for your Project 

Pro Tip: Size the valve by the flow rate required, not the pipe size of the valve. Most times you can go a pipe size or two smaller with a properly sized digital because the flow path through the ball element is less restrictive than a bigger brother thermostatic. Here are a couple of examples of what that could look like: