By Barry Stone
Dear Barry,
We are purchasing a 1910, 3-story home. Our home inspector said the house was previously heated by steam but has been converted to hot water. The problem, he says, is that the pipes were not changed. He explained that pipes intended for steam are not the same diameter as those installed for hot water and that this affects the efficiency of the system. The boiler is functional but will soon need replacement. When we replace it, should we convert back to steam heat or replace the piping to accommodate hot water heating? Also, is it feasible to add central air? -- Richelle
Dear Richelle,
Your home inspector's opinion and recommendation were accurate. The design and layout of steam pipes differ significantly from hot water heating systems, owing to the dissimilar characteristics of these two heat media. Inappropriate piping can reduce the efficiency and effectiveness of these systems.
Steam pipes must slope upward at the supply lines to prevent water in the system from restricting the flow of steam. Also, these pipes should decrease in diameter as they proceed away from the boiler. The return pipes must be smaller in diameter than the supply pipes, as they carry water instead of steam. Additionally, steam pipes need insulation on the supply side only: The return pipes should be uninsulated in order to promote condensation.
With hot water heating systems, the diameter of the piping remains constant, the slope is irrelevant, and all lines are insulated to prevent heat loss. Therefore, the house you are buying should have been repiped when the current system was installed. If you stay with hot water heating, the costs to complete the system conversion could be quite high. The piping would require replacement, and this could entail serious demolition and repairs to the interior walls and other portions of the home. What's more, replacement of the radiators, valves, and vents would be necessary if this has not already been done.
If most of the original system was left intact, restoration of steam heating would be advisable. For a specific comparison of costs to restore steam heat or complete the conversion to a hot water system, consult a licensed heating contractor in your area.
Central air cannot be added as part of a hot water or steam heating system, but a totally separate air conditioning system can be installed.
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