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Help with radiator shut-offs ('genuine Detroit')

Sorry this is so lengthy. I need help with radiators. No local person understands these. I've purchased an old Maine house w/oil-fired hot water radiators. (Local heating/plumbing folks tell me my house at one time had a gravity system, but currently is hotwater (pumped)). Each radiator has 2 pipes. They independently go into basement. Radiators have bleeder valves on the body of the radiator and shut-offs (see attached picture) on the inlet iron pipe. The problem is that in this 3-storey house, there is only 1 thermostat zone and I want to keep the heat down in some rooms on the 2nd floor because they get way too hot before bedrooms on 3rd floor heat up.

The radiator shut-offs only turn 1/2 turn. The knobs say "Genuine Detroit" on them. I've been told to basically leave the radiators alone (!) because of the possibility of leaks. But I've carefully turned one of them. It only turns 180 degrees. Full CW and full CCW both seem to be "ON". Setting them at the mid-point seems to create a slight leak!

Not all the radiators have exactly the same valves. Some have metal stops built into them to keep the knobs from turning more than 180 degress. Some do not have these stops, but turn only 1/2 turn anyway. (See the attached picture of the stops, where A points to a protruding rod that rotates when the knob is turned, and B to the stationary stop that this rod hits.)

One huge radiator that I would dearly like to turn off or down seems to have a totally non-functioning valve. I can take the knob off the shaft, and then remove a collar that has the stop protruding from it that keeps it from turning more than 180 degrees. When I do this, the knob is free to turn, and it turns forever. No setting seems to be 'OFF'. There seems to be a total disconnect between the shaft and whatever control is inside the housing.

The heating company says it would be very expensive to fix any valve, and have no certain knowledge of how these are even SUPPOSED to work. (One guy said it was a globe valve, whatever that is.) The entire system would have to be drained, and there is no guarantee they could even fix a valve. A pipe might break or the part may not be available. They say that even if they could fix it, after refilling the system, each radiator would have to be bled of air, and the old bleeder valves could break. I am hesitant to do ANYTHING, but would feel MUCH MORE comfortable if I only knew for sure how these valves were SUPPOSED to work.

One guy told me in the old days the valves had stops on them to keep renters (the house at one time was split into units) from turning a radiator completely OFF, but this seems bogus because if it were true the valves WERE only built to turn 1/2 turn, why did they bother with the stops?

I would like to know 1. how these valves were originally supposed to work; 2. what is the safest way to see if a given radiator can be shut off; 3. is it possible to just turn a radiator like these "down" or are the only choices ON or OFF? 4. For the one that leaks in the midpoint, should I wirebrush the paint off the nut on the shaft so I can tighten it to stop the leak, so I can test if the 90 degree setting IS the OFF position? Thanks very much to anybody who really recognizes this setup and can explain it to me. It's my mom's room that is too hot and she now insists on opening her window when the heat is on. I'm afraid this will be incredibly wasteful this coming winter.



  • Mark Eatherton1
    Mark Eatherton1 Member Posts: 2,542
    Generally speaking..

    shut off valves, when viewed from the top, are fully closed when in the clock wise position. THe valves you speak of have a small cylinder inside of a can that contains the cylinder. THe cylinder is cut such that if the valve is 1/2 closed, its apperture is 50% closed. Even in the full closed position, SOME water is allowed to pass through to avoid freezing and breaking the radiator.

    As for rebuilding them, that is usually limited to handle replacement, and sometime packing gland replacement. The internals are no longer made. They can usualy be replaced with some of the newer valves on the market (Watts Legend)but you still risk pipe collapse or other things.

    Good luck.

    Maybe you should consider an outdoor reset controller to limit the temperature fo availability...


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  • Dave Stroman
    Dave Stroman Member Posts: 763

    We work on these old radiators all the time. Most of those old valves don't work. Lots of times the stem has broken loose from the cylinder and just spins freely. Air vents seldom break and are easy to replace. Draining and refilling the system is time consuming but it is not the end of the world. Surely there is someone you can fine who knows old systems and is not afraid to dig in and do the repairs. The valves just simply need to be replaced.

    Dave in Denver
    Dave Stroman
  • Rory Sellers
    Rory Sellers Member Posts: 2
    Need clarification please

    Hi and thank you for writing.

    Is the reason for the little stops, then, to keep the valve from completely closing, as you say? Thus without the stop collar on, the knob turns a few more degrees than with it attached?

    Were these valves, then, originally designed to support any position between ON and OFF, so you could theoretically have the radiator only heat up, say, half as hot (e.g. instead of producing a delta temperature, to produce delta/2?)

    Any idea why the one valve I described exhibited a small leak in the midway position, but not at either extreme?

    Also, is the rationale for the outdoor reset controller you mention that if the water is kept at a lower temperature when the outdoor temps are higher, the radiators will heat up more slowly? Is this to allow the thermostat to operate more effectively?

    Thanks again.

  • Mark Eatherton1
    Mark Eatherton1 Member Posts: 2,542
    Clara Factation...

    The stops don't have anything to do with minimum flow. That's being done by a 1/8" hole drilled in the cylinder. If the valee is completely closed, it still passes water.
    The stops are just to show you where the valve cylinder is in relationship to open and closed.

    The ODR does as you say, essentially. It saves fuel, and increases comfort. Your boiler thinks its -10 deg F everytime the thermostat sends down a call fo heat. It knows no better. It can't "see" outside.


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