Banging in pipes

Valetta

We have recently have changed two radiators and due to the floor design changes it required additional elbows (90 deg) to make our way towards the radiators . We are getting constant banging as the steam comes up from the main raiser to the radiators.Is it the amount of elbows that required to make our way or the pitch on the return line. It is how ever a two pipe system on a second floor unit in a 10 floor commercial building.

Jamie Hall

Could be...

any of several possibilities.



Check the pitch of each section of pipe very carefully.  Each section must be pitched to drain -- either to the riser, in the case of a feed line, or to the return, in the case of the return line.  Even a relatively short piece of pipe, if pitched the wrong way, can cause a really bad water hammer.



Second, check the pitch of the runouts (both feed and return) from the steam main, if these radiators have them.  In the process of repiping, it is possible that they were allowed to droop and thus collect water.  They too must be pitched correctly.



In both locations you are looking for anywhere that water could pool, even a small amount.



The other large group of possibilities is that you could be having a problem with expansion noises -- as the steam pipes expand, they lengthen, and if they rub on something or try to push the radiators around, they will bang.