Need help. Steam heat. a couple of the radiators are knocking loudly..

[NBachers]

3. Put a level on top of the radiators and make sure they are tilted slightly toward the floor valve.

ALSO- Make sure the floor valve is all the way open. Here are the reasons:

1. Tilting the radiator slightly toward the floor valve allows the condensed water in the fins to drain back into the system. It doesn't need to be tilted much, just enough for the bubble to register. Otherwise, the water condensed into the fins gets pushed around by the steam and can cause banging.

2. Make sure the valve on the floor is open all the way. Trying to control the temperature by closing the valve part way only constricts the return water opening. It won't do anything to stop the banging.

If that doesn't work, there may be some problems with the return water pipe not being sloped properly, or filled with scale. Or, there may be connections near your boiler that are clogged with scale, impeding the flow of water. If the first two don't fix it, it may be time to trace the return water pipes to make sure they're flowing downhill, or have the connections at the boiler checked for clogging.