Cast iron radiator bleeder valve port(s)


I bought a small used cast iron radiator about 6 months (about 12 inches wide by 24 inches high). I finally connected it up to the hot water heating system in an apartment that I will be renting out.
But, when I went to bleed the radiator, I noticed that the bleeder valve is in the end of the radiator only about half way up from the floor (about 12 inches up). That means I cannot bleed the air out of the top half of the radiator. After thinking about it, I figured out that it probably used to be a steam radiator that had a steam valve at that height. I guess they replaced the steam valve with a bleeder port and called it a hot water radiator.
At the top of the radiator on one end in the corner there is a flat head screw going into the radiator. I am guessing that I could try taking out the flat head screw and replacing it with a bleeder valve there. Does that sound about right?
I am hesitant to mess with the screw. I don't know how hard it will be to get out although my first try broke a screwdriver tip before anything happened with the screw. I am thinking about heating the screw with a torch first before trying to get it out.
Any advice or suggestions would be appreciated.
I also thought that "there oughta be something" -- like a piece of small tubing etc. -- that I could attach to the existing bleeder valve from the inside that could be fed from there up to the top of the inside of the radiator. I assume that no such thing exists, but that seems like it would be a way to bleed the air from the top of the radiator rather than from the middle.
P.S. I also just posted this question at http://www.heatinghelp.com/forum-category/76/THE-MAIN-WALL .
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Its set for steam now, the top plug has to come out and will unless it rusted to bad then you drill and tap the other side, Ive taken out the top plugs to double vent for steam or use on water, If you leave it half full it will be less than 50% heat since the top holds water, it will just feel cold and do very little. If there is alot of paint use paint remover and a wire brush, try penetrating oil let it sit a day, then heat the radiator with propane, a big screwdriver to fit tight and a wrench on the screwdriver usualy makes it work, I havnt had any that didnt come out.
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Make sure that the screw you are planning on undoing at the top is not one that holds the whole assemblage of individual radiator sections together.
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wrote:

Make sure that the screw you are planning on undoing at the top is not one that holds the whole assemblage of individual radiator sections together.
+++++++++
Thanks. I'm sure about that part. It's just a screw that goes into the corner of one of the sections of the radiator and doesn't go all the way through to other sections.
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wrote:

Its set for steam now, the top plug has to come out and will unless it rusted to bad then you drill and tap the other side, Ive taken out the top plugs to double vent for steam or use on water, If you leave it half full it will be less than 50% heat since the top holds water, it will just feel cold and do very little. If there is alot of paint use paint remover and a wire brush, try penetrating oil let it sit a day, then heat the radiator with propane, a big screwdriver to fit tight and a wrench on the screwdriver usualy makes it work, I havnt had any that didnt come out.
+++++++++
Thanks. Everything you wrote makes sense to me. I can easily do most of it and hope for the best. I'm not so sure about me doing the drill and tap part if that becomes necessary since I've never done that before. But, hopefully I won't need to do that and the screw will come out okay.
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Next summer, when the system is safe to work on, you can get the screw out readily with some heat and an impact screwdriver. Spend $7 or so at Harbor Freight for this: #37530 or pay double that at a hardware store. Pro mechanics have used these for years, and it surprising that it is below the radar of so much of the public.
Joe
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That, by itself, will *not* depressurize the system.

No, you just need to worry about scalding water under pressure. If you don't understand what the possible sources of pressure are, you should not be attempting to do this yourself.
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wrote:

So, the system being open to atmospheric pressure won't depressurize the system? -- meaning having the pressure within the system be equal to the pressure on the outside of the system? You appear to be missing an understanding of basic physics here.

You appear to be mistaken about how the system actually works. Using your advice, one would never even be able to bleed the radiators in the system due to an irrational fear of scalding water under pressure. With all due respect, you appear to not know what you are talking about here.
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Obviously it will *eventually*. In the meantime, though, you're going to have a fair amount of pretty hot water in your lap unless you figure out what *else* you need to do to prevent that.

You appear to be completely unaware of what pressurizes the system.

You appear to be completely ignorant about how the system works. I have no hesitation at bleeding radiators in an operating system, but I do have enough sense to not attempt to remove a bleed valve without shutting it down first.

Like I said -- if you don't understand where the pressure is coming from, you should not be working on this yourself. You don't appear to understand some pretty basic concepts here.
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Doug Miller wrote:

I think I'll pass on getting into any further dialogue with you on this one. It seems like all you want to do is tell me the sky is falling and I don't know what I'm doing, and that I shouldn't be doing this because I don't know how the system works. I do know how the system works. I have worked on hot water and steam radiator systems before -- including changing radiators, redoing plumbing to systems that had frozen cracked pipes in properties I purchased, replacing valves, replacing circulator pumps, etc. And, for whatever it's worth, my undergraduate degree is in physics so I also understand the science behind it all.
The system is a low pressure hot water system. It is a one-floor system and all of the other radiators in the system are on the same floor and are horizontal metal fin radiators which are close to the floor level, and all are below the level of the bleeder valve that is half way up on this one upright cast iron radiator that is in the system. This one upright cast iron radiator has a shutoff valve. It also has the bleeder valve that is half way up. And, it has the screw at the top that I plan on taking out, and that screw is at the highest point in the entire system. Right now, the screw is in an air-only section of the cast iron radiator because the air cannot currently be bled out of the radiator due to the low placement of the existing bleeder valve. So, I can easily turn off the heat, turn off the valve to this one radiator, turn off the refill valve to the system, open the bleeder valve and drain what little water may come out of it, and then work on removing the screw at the top and see if there is a way to put a bleeder valve in where the screw presently is located. Both the science and the practical engineering aspects of all of this are really very simple.
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[snip]

Please note that this is the first mention in any of your posts of a shutoff valve for the radiator in question ...

.. and the first mention in any of your posts indicating the least degree of awareness that you need to turn even part of the system off ...

.. and the first mention of that ...

.. and the first mention of any awareness that the refill valve even exists, let alone of the need to close it.
So I think I can be pardoned for assuming that you didn't know what you were doing -- you certainly gave no indication of it. Quite the contrary, in fact, since you argued with me when I said it wasn't quite as simple as just removing the screw...
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Doug Miller wrote:

One valve won't help anyway. You need to block both pipes.
My radiators have a valve. They are made to control the flow rate, and thus amount of heat delivered. They do not provide a tight seal.
--
bud--

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02/15/2010 -- Here's the final outcome.
I worked on the radiator today. I tried heating the screw etc. and I still couldn't get it to come out. After cleaning it off, I could see that it was more like a cylindrical set screw and it was sticking out enough for me to try using pliers to grab the part that was sticking out and try turning it that way. That also didn't work, but that revealed that the "set screw" was somewhat soft and was maybe made of brass.
So, that gave me the idea that maybe I could try drilling into the center of the screw and then use one of those screw removal tools. I went to Ace Hardware and bought the screw removal device and also bought a new bleeder valve.
The screw removal tool worked like a charm -- I just drilled into the center of the screw, then inserted the screw removal tool and the screw came back out fairly easily. Then I screwed in the new bleeder valve and bled the radiator and it's working fine.
Thanks for all of the suggestions and ideas.

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I have a situation with the same scenario and the radiators parts that have the bleeder only allowed water to go into those sections the other section s I would have to put a bleeder valve on each one get the water to come all the way up to it when you try using the steam radiator for a hot water sys tem
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