CircuitSolver Union Assembly (CSUA)

CSUA Banner - CSUAThe CircuitSolver® DHWS thermostatic balancing valve automatically and continuously balances a recirculation system in a fraction of the time compared to traditional manual balancing methods.

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

How It Works:

Using our unique Thermoloid® blend paraffin wax actuator technology, the CircuitSolver® Union Assembly valve is installed at the end of each branch or riser to monitor the water temperature in the line. It will automatically modulate open or close in response to changing temperatures to maintain a specified temperature.

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 to establish flow when it drops below the set-point. This automatic response to temperature allows the balancing valve to dynamically adjust to the varied usage rates in a DHWS throughout the day.

The CSUA 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 303 stainless steel
2 Union Nut 303 stainless steel
3 Female Threaded Inset 303 stainless steel
4 Plug 303 stainless steel
5 Operating Spring 302 stainless steel
6 Thermal Actuator 303 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 have hot water readily available 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



  • 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

We’ve used CircuitSolver®s exclusively now for several years in every application we can. Simply stated, the product is easy to install and works very well with no issues to date.

— Christopher Meurer - J.C. Cannistraro, LLC