How to drain cast iron rads to fix a crack?

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Rotty20

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Need to either partly or fully drain a cast iron heater in order to fix a Crack on top. But I'm not sure where to drain it from. From the purge valve on the heater or from the lines in the basement going to the furnace? Thanks in advance.
 

WorthFlorida

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You need to shut down your furnace and allow it to cool down. May take a few hours. There is a shutoff valve to the furnace to remove the water pressure. It might be were the PRV is.

There should be a spigot some where near the furnace to drain the system. If you have an old system that has a metal tank expansion, non bladder type it should be drained once a year. You can drain the system from there.

If the system is completely cold and the rad is on a second floor, disconnecting it without draining is ok. Only the water in the rad would all there be. You can stuff a rag in the pipes to hold back any water. It not

Draining the system can be a headache to get things working again since you have to know how to purge the air from the system. Replacing the one radiator also will need to purge the air.
 

Rotty20

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You need to shut down your furnace and allow it to cool down. May take a few hours. There is a shutoff valve to the furnace to remove the water pressure. It might be were the PRV is.

There should be a spigot some where near the furnace to drain the system. If you have an old system that has a metal tank expansion, non bladder type it should be drained once a year. You can drain the system from there.

If the system is completely cold and the rad is on a second floor, disconnecting it without draining is ok. Only the water in the rad would all there be. You can stuff a rag in the pipes to hold back any water. It not

Draining the system can be a headache to get things working again since you have to know how to purge the air from the system. Replacing the one radiator also will need to purge the air.
Thank you so much. I'll have a look and see but it is on the 2nd floor above the basement. Don't recall a tank down there though. Would be nice to cut the pipe right below it.
 

WorthFlorida

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Thank you so much. I'll have a look and see but it is on the 2nd floor above the basement. Don't recall a tank down there though. Would be nice to cut the pipe right below it.
All hydronic heating plants have an expansion tank.
 
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