I think that by "flushing" I mean the same thing as you mean in "blowdown."

Daily? No one ever suggested that often before. The guy who installed it
suggested weekly.

I've never been clear what the "blowdown" does anyway.

-- Ray

"Edwin Pawlowski" wrote in message
news

"Ray" wrote in message
news:rL6gj.1104$EN6.1069@trndny07...
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?

Banging steam pipes come from water in the pipes being shot by the flowing
steam. Dangerous? Usually not on a low presure system, certainly on a
high pressure system. The water can be condensate laying in pipes that
are not properly pitched, or it can be "carry over" where the steam picks
up water from the top of the water and carries it into the pipes and slams
it into the fittings at elbows and such. Filling too high can cause that
also. I've seen 12" steam pipe bounce and shake violently from water
hammer. It can also break open or fitting fly off. Try to avoid it.

You may want to consider how you perform the maintenance. Instead of a
weekly flushing, a daily blowdown is peferable. There is no sensible
reason to do a flushing as you are just adding fresh water and all the
oxygen it contains. You want to flush the minerals that condense out by
doing a blowdown of the bottom of the water chamber. If you have a lot of
minerals, a softener would be a big help. Most industrial boilers also
have water treatment to reduce oxygen and scaling of the tubes.
Residential cast iron boilers usually don't do that.

If it continues, get the advice of a professional that knows steam and how
the system works. Get your water tested.