CircuitSolver Union Assembly (CSUA)

CSUA BlueBackground Product Page Image - CSUACircuitSolver® valves balance a domestic hot water recirculation system in a fraction of the time and dynamically modulate flow to sustain a set water temperature by automatically balancing the system as conditions change.

The CircuitSolver® Union Assembly (CSUA) features a union with an optional check valve built into the body of the CircuitSolver® and isolation ball valves on either side to reduce the number of system components installed, minimizing potential leak points. The CSUA valve has an integrated O-ring in the union and is factory assembled for a leak-free seal.

These thermostatic valves eliminate the need for costly labor, repeated callbacks, and manual “guesstimate” calculations of system projected usage. Instead, you have a dynamic solution that responds to the needs of the building and constantly modulates flow to maintain a set temperature.

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How It Works:

The CircuitSolver® Union Assembly valve is installed in a domestic hot water system just before the return at the end of each branch or riser. The valve uses our unique Thermoloid wax thermal actuator to modulate between open and closed in response to temperature changes to maintain a specified temperature in each line.

The valve will be in its closed* position when the water temperature in the supply branch is above the valve’s set-point and only open, establishing flow when it drops below the set-point. This automatic response to temperature allows the balancing valve to adjust dynamically to the varied usage rates in a domestic hot water system (DHWS) throughout the day.

*Note: The valve will never fully close, allowing a small flow bypass to the return to avoid dead-heading the recirculation pump. The limited flow to your return line will reduce system wear, electricity, and water usage and improve overall system operation.

Valve Components:

The CircuitSolver Union Assembly valve comprises 100% stainless-steel components, a high-quality O-ring, two isolation ball valves, and an optional check valve.
CSUA callouts 1024x246 - CSUA

1 Valve Body w/ Union Threads 300 series stainless steel
2 Union Nut 300 series stainless steel
3 Female Threaded Inset 300 series stainless steel
4 Plug 300 series stainless steel
5 Operating Spring 300 series stainless steel
6 Thermal Actuator 300 series stainless steel
7 O-Ring Buna-N
8 Check Valve (Optional) Glass Filled Noryl
9 Ball Valve, ½” MxF Brass Lead-Free

Typical Applications:

The CircuitSolver® Union Assembly can be used in any building with a domestic hot water recirculation system to ensure it’s thermally balanced and readily available hot water at each fixture. Used in commercial buildings of all sizes and DHWS’ with varying complexity, installations often include hospitals, schools, hotels, high-rises, and multi-family apartment buildings.

To see CircuitSolver® installations in your area, visit our installations page.

CircuitSolver® thermostatic balancing valves can also balance the return flow between the master mixing valve and the water heater. To learn more about this application, go to the Balancing a DHWS Return with CircuitSolver page.



  • Automatically and continuously adjusts to balance domestic hot water systems
  • Eliminates balancing labor and callbacks
  • Direct replacement for manual balancing valves
  • Reliable, long-lasting thermal actuators
  • Long service life and 3-year warranty


  • NSF/ANSI/CAN 61 & 372 Certified
  • Lead Free
  • Fully compliant with Section 1417(d) of SDWA, the Safe Drinking Water Act
  • Supports efforts toward LEED Certification
  • Complies with the Buy American Act


  • Sizes: 1/2″, 3/4″ & 1″
  • Fixed Temperatures:
    • 100°F (37.7°C)
    • 105°F (40.5°C)
    • 110°F (43.3°C)
    • 115°F (46.1°C)
    • 120°F (48.8°C)
    • 125°F (51.6°C)
    • 130°F (54.4°C)
    • 135°F (57.2°C)
    • 140°F (60.0°C)
  • Max Working Pressure: 200 PSIG/14 BAR
  • Max Working Temperature: 250°F/121°C
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