How to Adjust a Taco Automatic Fill Valve


Taco makes a number of valves and control mechanisms for heating and cooling (HVAC) systems and applications. One such valve is the boiler auto fill valve which allows a supply of pressurized water to pump into the boiler before being sent through the system pipes. Systems such as hot water radiator heating utilize this type of setup. While for many systems the default Taco settings are sufficient, in some buildings this pressure may be too low to properly propel water through to the higher level radiators on upper floors. This requires an adjustment to a higher psi.

Things You'll Need

  • Schematics of building where boiler is located (optional)
  • Wrench
  • Flathead screwdriver
  • Locate the Taco Automatic Fill Valve near the top of the boiler, near the drain pipe and shut-off valve. On the front of the valve unit, locate the gauge and adjustment locking screw.

  • Note the number shown on the gauge. This number is the current psi that the system is set to deliver water into the boiler at. The Taco system is, by default, set to 12 psi but may need to be set higher if radiators on higher floors are not receiving water flow.

  • Verify that the "Fast Fill" lever is locked into place next to the "A" on the side of the valve control. This is the normal operating position for the lever.

  • Calculate the required psi setting for the building the boiler is in. Determine the distance in feet from the valve itself to the highest level radiator in the building. You may need to see the building schematics to determine this. Multiply the number in feet by 0.43. Add 3 to the total.

    For example if the distance is 150 feet from valve regulator to the highest radiator multiple 150 * 0.43 = 64.5 + 3 = 67.5.

  • Use the wrench to slightly loosen the locking nut on the adjustable center screw.

  • Use the screwdriver to slowly turn the adjustable center screw clockwise. The gauge number will increase. Continue turning the screw until the gauge displays the desired psi determined from the calculations in Step 4.

  • Retighten the locking screw to complete the adjustment.

Tips & Warnings

  • According to Taco, the valve has a maximum supply psi of 100. Do not exceed this number.
  • Do not attempt to make the adjustment with the "Fast Fill" lever in the override position (opposite of the "A" position).
  • The boiler, valve, and surrounding pipes may be hot to the touch.

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  • Photo Credit white radiator image by Ekaterina Sidorenko from
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