Clanging pipes in steam heat system

it was working fine until we recently put in a new radiator. Now it's loud enough to wake us all out of a sound sleep. Is this an ordinary plumber issue or do we need to call someone else (boiler service)? TIA

Banging and knocking?

Assuming steam heat, ask whoever you call if they have experience with steam.  As a quick check, make sure the valve on your new radiator is all the way open with just a very slight turn back towards closed.  A partially closed valve can cause banging.

mrmaplewood said:

Banging and knocking?

Yep

Did you try to flush it? That is, did you run off some water from the boiler? My radiators bang LOUD when there is too much water in the system.

this is helpful! We'll try this tonight!

Is it steam heat or hot water circulating? Steam has the bulb-like thing on the end of the radiator.

steam

We suffered the from the same after renovations altered the slant of a return pipe.  And I mean banging that would wake the dead.  A plumber I got from Maplewood online,  Mark Bleiweis (908-686-7415), diagnosed and fixed after two other plumbers could not.  Peace at last.....

Tonight, when I got home the radiator in the kitchen was banging (that's where it starts). I emptied a few buckets out of the system and even though the auto fill kicked on a few minutes later, the radiator stopped banging immediately. I have steam as well.

@OP,  there's some add'l info that would be helpful.  You spoke of a new radiator- is this in fact the source of the noise?   is this additional or a replacement radiator?   Where in the line is it located?  closest to boiler?  furtherest?  middle?    Has distribution of heat been effected?

It's called a "water hammer". -Water lays in the radiator and when the steam comes up it slams it against the inside of the radiator.

Incorrect pitch of the radiator is one of the most common culprits. Does the new radiator pitch slightly downward towards the pipe where the steam comes in? (and where water drains out after it cools). If not, you will need to correct. Believe it or not you can slightly lift what should be the high end and put a small shim under those legs. (I'm talking about an 1/8th inch). There is almost always enough flex in the pipe to do it if you have or can get help to muscle it up.

If you Google "steam system water hammers" you will find other ideas.

It usually has more to do with pitching of the branches to the radiators, excess pressure, and return lines that are slow to drain back to boiler. Often the place the problem presents itself (as water hammer) is remote from the area that causes it.
Here's a thermal image showing a pipe being reduced and backpitched on a horizontal main in a Maplewood home. The funnel being created by the dissimilar pipes is pooling water, here represented by the darker bottom of the pipe on the right side of the fittings. That pooling created tremendous water hammer until we were able to straighten the whole thing out.