The Holby Valve Company offers the first and most-widely specified water tempering valve in the industry. The Holby tempering valve is a temperature regulating valve, designed to be used as a master, zone, fixture or individual appliance regulator to control the predetermined temperature of hot water. Water delivered from hot water generating equipment such as storage tanks, heat exchangers, submerged coils, or any other source, is frequently too hot or scalding. This condition can be corrected by the installation of a Holby tempering valve. It is a necessary part of any submerged tankless water heating system.

The Holby tempering valve is also used in regulating temperatures for engines, heating systems, compressors, cooling towers, processing machinery and many other applications. Please note: IT IS NOT AN ANTI-SCALD DEVICE.

  • Rugged, constructed entirely of bronze and copper and hydrostatically tested to a pressure of 300 pounds.
  • Adjusts to deliver water within close tolerances of any temperature 120 degrees Fahrenheit and below.
  • Temperature of water delivered by the valve can be changed by turning the adjusting screw to the right or clockwise for lower temperatures; and to the left or counter clockwise for higher temperatures. It will maintain a uniformed desired temperature regardless of the temperature of incoming water. To facilitate adjustment, a thermometer should be placed in the outlet line beyond the Holby tempering valve as shown in the diagram and water should be flowing through the valve when adjustment is being made.
  • Long mixing chamber with vanes at an angle to the longitudinal axis of the valve which causes a thorough mixing of the hot and cold water.
  • Unusual length of the hydraulic thermostatic element, assures effective surface contact with the water.
  • Thermostatic element is placed in the body of the valve where the hot and cold water mix. It is immediately sensitive to any change in water temperature and makes proper corrections by opening or closing the hot and cold water inlets in the valve.
  • Sensitive parts of the thermostatic element are inside a heavy non-ferrous tube which protects them from any corrosive or scaling action caused by the continuous flow of water past them.
  • Extraordinary length of the thermostatic element provides fifteen to twenty times the number of corrugations found in the usual short thermostat. Thus, the total expansion is divided over these numerous corrugations, so that the flexing of each is reduced to mere thousandths of an inch with resulting long life of the instrument.
  • Action of the thermostatic element moves a piston over the hot and cold water openings, opening the cold as it reduces the opening of the hot, thus uniformly blending the hot and cold water, producing an even temperature of the delivered water without any change in volume. This action eliminates the building up of temperature in circulating systems at times when little or no hot water is being used.


The Holby tempering valve will operate satisfactorily when installed in any position WITHOUT TRAPPING. It can be installed with a minimum number of extra fittings, reducing installation costs to a minimum. Its extraordinary length takes the place of expensive brass pipe. When installing, the basic piping diagrams should be followed for the warranty to be effective. (See Manuals Tab Above)

The end of the valve, where the adjusting screw is located, should NOT be placed against, nor in line with any other fixed object for a space of twenty-four inches. This will allow access to the inner parts of the valve, if necessary.

NOTE: Size of hot water inlet and mixed outlet end determine the size of the Holby tempering valve.
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Thermostatic Element Length:
Max Temp (F):
Max Pressure (PSI):
Point of Source
Standards Met:
ANSI 1017
ASSE 1017
1 Year
Product Type:
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