Thanks -- This very loud 'knock' has happened only once, so far as I know.
It happend shortly after I did a flush or 'drawdown' -- I wonder if it might
have been a one-time problem.


"Bubba" wrote in message
...
In short, everything from the radiators to the boiler has to have the
radiators and piping with a slight pitch back to the boiler. This
includes all of the piping. Even that hidden in walls and floors. Not
always the easiest of fun jobs.
A bad steam trap at the radiator or in the lines can cause this
problem too.
Bubba

On Sun, 06 Jan 2008 19:23:16 GMT, "Ray"
wrote:

Yes, ours is a single-pipe system delivering steam.

But what do I do about the "knocking" problem?


"Bubba" wrote in message
. ..
On Sun, 06 Jan 2008 15:48:39 GMT, "Ray"
wrote:

Sorry to be such a pest, but I have another question about our aging
steam
radiator system in our six-unit apartment building. Last night, an hour
or
so after the weekly flushing of the systerm, we heard a very loud knock
in
the pipes. As if someone had hit the pipe with a sledgehammer.

Is this dangerous? What should I do? Was the knock, which we heard only
once, probably tied in with the flushing?


You most likely have a one pipe steam heating system. The "knock" was
steam hitting the cold condensate water coming back the same pipe.
Yes, it can be VERY destructive.
Bubba