Hot Water Heating


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P-K COMPACT Semi-Instantaneous Indirect Water Heaters

Models: PK06, PK08, PK10, PK12

P-K COMPACT® semi-instantaneous water heaters perform reliably, providing long, trouble-free operation in thousands of installations.

Its design, which focuses on small heaters that produce high volume output at a closely controlled temperature, makes it an ideal water heater for almost any building owner.

History of Performance


P-K COMPACT® semi-instantaneous water heaters have performed reliably, providing long, trouble-free operation in thousands of installations in all types of commercial, institutional and industrial buildings. Its present design, which focuses on a small heater that produces high hot water output at a closely controlled temperature, makes it the ideal water heater for any building owner.

High Output Heater

To serve your needs

Operating on steam, boiler water or high-temperature water, the P-K COMPACT® produces up to 250 gpm at 40°F to 140°F. Though the largest unit has a footprint of only 8 sq. ft., the heater can handle any building’s water heating requirements, either singly or via multiple-unit installation.

Prevents Scale

Preventative measure

Constantly pumped circulation prevents scale formation and accumulation of foreign matter on the heating surfaces in most water conditions (water softening may be required with extremely hard water). The constant circulation also continually monitors water temperature, stabilizing temperature control at all draw rates.

Constructed for Long Service Life

Reliable and durable

The P-K COMPACT® is built to last. Potable water in the shell contacts only nonferrous materials, preventing rusty water. The shell is constructed of solid 90-10 copper nickel, the premium corrosion-resistant material for potable water service. Standard heat exchanger construction is copper tubing, which will handle most water conditions. Copper nickel is available for unusual water conditions.

Featuring Harsco™’s proprietary ANTICIPATOR® control, the outlet temperature is continuously monitored such that the system can immediately respond to hot water demand, even with fluctuating draws, to a close tolerance of ±4°F of set point. Constantly pumped circulation stabilizes temperature control at all draw rates, continually monitors water temperature, and prevents scale formation in most water conditions.


  • High quality design and construction
  • Complete package with only four piping connections
  • High capacity output
  • ANTICIPATOR® temperature control regulates hot water outlet temperatures ±4°F
  • Constant circulation by the pump improves temperature control and minimizes scale
  • Copper-nickel shell, naval brass tubesheet and optional copper (copper nickel) preclude rusty water
  • Double solenoid temperature-limit system prevents overheated water from entering the distribution system
  • Meets seismic Zone 4 requirements
  • Built to ASME standards; meets code requirements
  • Meets BOCA and IAPMO code requirements
  • Heat transfer rates verified by independent testing agency


  • Unique double bolted tubesheet construction allows for quick inspection
  • No overhead room required for service
  • Reliable performance and long service
  • Quick, easy installation
  • Saves valuable floor space
  • Meets the hot water requirements of almost any building
  • Performs equally well with steam, boiler water or high-temperature hot water



For more information about this or any of our other products, please contact us or click here to find your authorized Harsco Industrial Patterson-Kelley representative.


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