P-K COMPACT® Semi-Instantaneous Indirect Water Heaters

Models: PK06, PK08, PK10, PK12

A History of Performance

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

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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

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.

ANTICIPATOR Control System Produces Close Temperature Control

The P-K Compact water heater features the ANTICIPATOR integral control system which meters the heating medium demand to exact proportions of hot water requirements and regulates hot water outlet temperature to a close tolerance of ±4°F from the set point. Steam passes through the tubes of the heat exchanger bundle. The water is rapidly heated as it is directed over the tubes by segmental baffles inside a cylindrical wrapper. Above the wrapped tube bundle, minimum storage volume is provided to give the control sufficient time to produce the close temperature control.


  • High capacity output
  • ANTICIPATOR temperature control
  • Copper-Nickel shell, naval brass tubesheet
  • Copper-Nickel (standard), Copper, and Stainless Steel (single wall only) tube bundles available
  • Complete package with only four piping connections
  • Constant pump circulation improves temperature control and minimizes scale
  • Electric, Pneumatic, and Self-Contained control valve options available
  • Optional stand available to meet seismic Zone 4 requirements
  • Optional pump trim available to incorporate building recirculation flow within COMPACT® circulation pump capacity
  • Optional high pressure tube bundle and/or shell rating (up to 400psi)


  • Saves valuable floor space
  • No overhead room required for service
  • Meets hot water requirements in most buildings without the need for additional hot water storage
  • Performs equally well with steam, boiler water or high temperature hot water
  • Improved valve performance and capacities, configurable to suit customer requirements.

Contact us to learn more about the Patterson-Kelley difference.

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