[Shop-talk] Removing a small hot water radiator

[John P. New]

Jim,

I have a large hot water radiator system (about 40 radiators) in my home, and I have removed and replaced a single radiator many times without draining the entire system.

First, shut off the boiler, the supply water to the system and the recirculating pump. Go to the lowest point on your system that has a drain valve. In my system, and I think normally, this is at the boiler. Open the drain valve and start draining the water. At the same time, occasionally open the bleed valve on the radiator to be removed to see if there is still water pressure at that radiator. If there is, close the bleed valve and wait a bit, and then open the bleed valve again. At some point, the bleed valve will start sucking air. Leave the bleed valve open until the radiator is empty of water. At this point, close the main drain valve at the boiler.

How will you know when the rad is drained? When the water noises in the rad stop, it's a safe bet that it's empty. After you close the main drain valve, partially undo the pipe connections to the rad to make sure it's really empty. If no or very little water comes out, it should be safe to remove the radiator. Put notes on the system supply water, the boiler control and the circulating pump not to turn any of them on until the rad is put back!

Make sure you have plenty of old towels on hand to catch any rad water _before_ it spills; old systems with cast iron radiators can have some very nasty black water that stains everything from fabrics to tile and marble.

Hope that helps.

John

On March 14, 2012 11:30:35 AM Jim Stone wrote:
> I am in the midst of remodeling a bathroom and need to remove a small radiator
> that was installed in a previous remodel.  The radiator small kick space unit
> like this: http://www.accentshopping.com/product.asp?P_ID=150766.  We are
> going to  put electric radiant heat under the tile, so the old system (which
> was totally under-sized for the bathroom) is no longer necessary.  However, as
> long as we have the lines there, we are going to install a hydronic heated
> towel rack near where the old radiator sat.  I'll need to cut the old copper
> pipes below floor level and route them into the walls.  That part should be
> pretty straightforward and fortunately, we probably won't need the heat again
> this season.  Therefore, the plan is to simply do the rough-in now and cap the
> pipes.  Should we get a prolonged cold snap and need the heat, I will put in a
> jumper across the inlet and return, but I don't think that will be necessary.
> 
> So, that is the background.  My question is around removing the old radiator.
> The bathroom is on the second floor, which has four other cast iron radiators
> on it.  For what it is worth, this one is the farthest from the boiler.
> Should I completely drain the system, or is it enough to simply drain a little
> to release the pressure and drop the water level?  The system hasn't been
> drained in the five years I have lived here, so if this is a recommended thing
> to do anyway, I guess now is as good a time as any.
> 
> Thanks.
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