Help! Cast Iron Radiator Is Cold! How Do I Get Them To Work? - Plumbing - DIY Home Improvement | DIYChatroom

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Old 10-13-2009, 04:30 PM   #1
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Help! Cast Iron Radiator is cold! How do I get them to work?


My heat is with cast iron radiators! This is my 3rd winter in this house. The first winter everything worked great! The 2nd winter all radiators started out ok but by the end of the winter 2 of them stopped working. Now this year I started the unit and all of the radiators on the 2nd floor don't work.

I have a total of 7 radiators. 3 on the main floor and 4 on the 2nd floor.

I have tried to bleed the radiators but nothing happens. The 1st floor radiators had no air in them and just spit out water. That is good! The second floor radiators started with the the air hissing sound but never any water coming out of the bleed valve.

So - I am confused at why the system is not working. I have done quite a few google searches to try and figure this out but nothing seems to be working.

My boiler is in the basement. It has the expansion tank on top of the boiler. The unit is heated by natural gas.

My expansion tank seems to have a lot of water in it. Is this normal?

There does not seem to be a circulation pump. I think this unit is all gravity. There is a small red thing that is connected to the hot water heater and the cold water intake. I believe this is for an auto refill of the system.

Anyways, I need help. It is very cold upstairs and the bedrooms are all upstairs.

Can anybody help me?



duchesslana is offline   Reply With Quote
Old 10-13-2009, 05:29 PM   #2
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I had a radiator that was about empty
It took quite a while to bleed all the air out
If air is coming out that means there is pressure to the radiator
So keep bleeding it until you get water

It is possible the pipe is clogged up....but if it was working the 1st year...


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Old 12-19-2009, 08:02 PM   #3
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There should be a guage on the front of the boiler. It wiil tell you what the temp is and what the pressure is. It should have around 12psi on it, sometimes you may need to increase the pressure to force the air out. But you need to be careful not to raise it to much or you will blow the relief valve.
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Old 12-19-2009, 08:12 PM   #4
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If you have a manual fill valve you may need to open it while you bleed the radiators.
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Old 12-20-2009, 06:54 AM   #5
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You want to somehow start with the expansion tank empty of water. This can be difficult unless there is a shutoff valve under the tank to keep water from the rest of the system upstairs from refilling the tank (or getting all over the floor) as you try to drain the tank.

When the air valve at the top of the tank is closed and the system is put back together and properly refilled, some water will re-enter the tank.

An alternative to taking the tank off and emptying it out is to pressurize it fromt the valve on top. You will need to follow the instructions for your system and have a gauge to measure the pressure with.

It is possible that you may have to alternately add more water to the system and bleed a radiator a little several times before the (upstairs) radiator is (properly) full of water.

With insufficient pressure in the system, the radiator bleed valve will suck air in instead of spit it out. A piece of toilet paper can be used to tell you which is happening.
The good conscientious technician or serviceperson will carry extra oils and lubricants in case the new pump did not come with oil or the oil was accidentally spilled, so the service call can be completed without an extra visit.

Last edited by AllanJ; 12-20-2009 at 11:43 AM.
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Old 12-21-2009, 02:42 PM   #6
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Go to Post your problem to 'the wall'. Lots of experts on hydronic heating.


If I could only remember to THINK about what I was doing before I did it.
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bleeding , boilers , cast iron radiators , expansion tank , heating

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