how to clear old cast iron rads?

steamersDad

Oldest son has a turn of the century Victorian with some lovely old cast iron Rads. We suspect there may be plugging in a couple, as they only get warm in the first couple sections past the valve. Any suggestions for internal cleaning?

BobC

Radiators not heating

If this is happening on light heating days it may be more a matter of balancing the system venting so steam gets to all the radiators at about the same time. Does the inlet of this radiator get hot around the same time as others that are about as far away from the boiler?



Is this radiator at the end of the main? If the mains venting is too slow that could explain it.



Have you checked the air vent (assuming it's single pipe steam)or the steam traps (two pipe steam). The air has to leave the radiator before the steam can fill it. If it has air vents on the side of the radiators try swapping the vents from a radiator that heats ok and see what happens.



If the radiator really is plugged up it has to be removed and flushed out. That is a lot of work so try to eliminate everything else first.



Look through the articles on this page to see if anything there makes sense.



http://www.heatinghelp.com/article-categories/16/Steam



Bob

Jamie Hall

It's really uncommon

for a steam radiator to plug up -- the passages inside are huge (relatively speaking) and they are at both the top -- which would be almost impossible to plug) and at the bottom, which is only slightly less likely to plug.



Furthermore, if the radiator is heating at all, it means the steam can get in.  If the steam can get in, the air can get out!  You don't say whether this is one or two pipe, but in either case the air has to go somewhere.



From your description, I'm going to go with BobC: it is much more likely that these radiators just don't get steam as fast as some of the others.  For which there is a book full of reasons, and the selection of reasons depends somewhat on whether it's one pipe or two pipe.  Venting applies to either one -- both vents on the radiator, if it's one pipe, or the vents on the mains in either case.  On two pipe, is it possible that the valve is somewhat closed?  That could do it.  And so on. 



Tell us some more...



And don't start taking things apart to try to clean them until you've looked at pretty much everything else!