Harold Kestenholz
Good points Sylvan.
I suspect circulator failure in this probable gravity system is partly from being driven by the water after the heating cycle and partly by running without a back pressure.
A quality flow control valve more like a pressure reducer, or a large zone valve can also stop the water from moving after the heating cycle. Some of these old systems would keep a flow control valves in the open position from their own gravity power.
An injection system into a joined supply/return will also make the circulator controllable.
I agree that the system should be treated as a sealed system to prevent unneeded corrosion from frequent addition of fresh water. The old tank-in-the-attic hand filling technique told the owner that there was a leak by more frequent refilling fequirements. Automatic does not always mean good.
The balancing cocks may be there. If so, then balancing the system will be a great help toward comfort. On the downside, the plumber-engineers who supervised the older systems balanced the system by tricks in pipe sizes and joining the main above, to the side, and below the main, the cocks might not be there.
90 years ago, 1910, thermometers were a valuable device not to be left on the job, so the taps for them might not be there; but it is simple enough to introduce them.
Sylvan, I hope there is someone nearby this owner with your knowledge to help correct these problems. This is fun.
