Piping an Indirect Tank into a Steam Boiler

Piping an indirect or baseboard to a steam boiler


Caution: All drawings are conceptual drawings for illustration purposes only and may be incomplete. More specific drawings may be needed for your application.

Piping an indirect water heater into a steam boiler is not an uncommon application with gas or oil-fired steam boilers. There are a few bits of information we need to talk about before we do the piping.

For more information sizing steam boilers when adding HW baseboard and/or indirect water heater options

  • We can return the water from the indirect to a boiler taping normally in the opposite end of the boiler from the supply. This will avoid short cycling of the water within the boiler. If you pipe into the steam system return pipe the pipe must be on the boiler side of the hartford loop.
  • The boiler should have at least one 1" or larger tapping higher in the boiler than the return tapping.
  • Use an aquastat to keep the boiler from creating steam on a demand for DHW or HW baseboard onlyA seperate control taping in the boiler and slightly higher than the IWH pipe taping works best.
  • The control taping can be as small as 1/2" for the control well. A strap on control on the piping works and is a bit harder to stop the boiler from steaming. A control in the boiler is much more accurate.
  • It is best to use a bronze or stainless circulator to pump this water. Although many have used the smaller wet rotor circulators, it is best to use a three-piece circulator. The circulator must pump away from the boiler. Think of the boiler as the expansion tank connection
  • The piping from the supply tapping must elbow down toward the floor and mount the circulator close to the floor to keep the live steam away from the inlet of the circulator in case of surging water. If steam enters the circulator it can cause the circulator to fail.
  • It is a good idea to install a strainer before the circulator as some dirt my get disturbed in the bottom of the steam boiler with the circulation of water. We wanrt to keep the debris out of the circulator, radiation and/or IWH coil.
  • The use of a check valve is recommended

Click to see drawings

Disclaimer: The information found on this website is for informational purposes only. All preventive maintenance, service, installations should be reviewed on a per job situation. Any work performed on your heating system should be performed by qualified and experienced personnel only. Comfort-Calc or it's personnel accepts no responsibility for improper information, application, damage to property or bodily injury from applied information found on this website as it should be reviewed by a professional.