Semi-Instantaneous Hot Water Heater Systems

Steam to heat semi-instantaneous water heaters, the envirosep SIWH, are specifically designed and manufactured for hot water systems with intermittent loading. The system is designed to heat water, on-demand; and a small storage tank is utilized to buffer sudden surges, resulting in accuracy to +/- 3 deg F. An internal circulation pump is provided to obtain an even temperature profile throughout the tank volume. The Envirosep SIWH may be manufactured to include a system recirculation pump, which is recommended for maintaining hot water loop temperature. Electrical controls may be provided with PLC programmable controllers or simple, relay logic.

The Envirosep negative pressure semi-instantaneous steam-to-water heater, envirosep NSIWH, is a manufactured, ready-to-install system designed to address the requirements of commercial potable water heating systems. Designed for high thermal efficiencies under varying load patterns, this system utilizes a fully modulating variable Pilot-operated temperature control valve capable of handling steam pressures ranging from 5 to 150+ psig. This system operates below 0 psig*, delivering a reduction in energy consumption of 15-20%. Capable of handling a wide range of water flowrates and temperatures, while being custom-tailored to your specific site needs, makes this system an ideal choice for either new or retrofit installations.

* Note: Under most service conditions which are typical to potable water service.


  • ASME, Stainless steel hot water buffer tank,with U-stamp
  • Self-contained, pilot-operated or pneumatic modulating steam control valves
  • High temperature cut-off switch, for independent source steam isolation
  • Secondary high temperature purge system, with blowdown controls
  • Internal circulation pump
  • UL Listed NEMA 12 industrial control panel
  • Float & thermostatic steam trap
  • Outlet temperature indication
  • Safety relief valves
  • Removable tube section
  • Inlet Steam Condensate Removal
  • Pump/Trap with Receiver (envirosep NSIWH)


  • PLC System controller w/ touch screen
  • NEMA 7/9 explosion-proof rating
  • Inlet steam condensate removal
  • System recirculation pumps (including horizontal installations)
  • Steam-powered or electric condensate pumps
  • Multi-staged centrifugal pumps
  • Auto system flow activation
  • Plate & Frame Heat Exchangers
  • Stainless Steel Main Headers
  • Filtration
  • Specific performance criteria (upon request)
packaged pumping systems
industrial control panels

Contact us to learn more about Envirosep solutions.

We offer integrated solutions for your fluid handling, heat transfer and energy recovery needs.