Piping

sooner302

I have a one pipe steam system in a 4-unit apartment.The last 30ft of return to the boiler is 2-inch copper.Its connections,on both ends are cast.Its my understanding that this causes electrolysis.I was planning on isolating this copper by installing schedule 40 PVC.Will this work,or am i waisting my time?? secondly,since electrolysis has been evident,should i be concerned about plating in the boiler, or any place else.

Oak Park Electric

Don't do it

Plastic pipe has no place in any steam system.  It will soften and sag, the joints will fail, etc.  It could potentially leach chlorides into the water and put a hole in the boiler. It seems to be accepted here to connect copper directly to steel or cast, but only for heating.  Not like domestic water where you need separation.  A brass fitting, nipple, valve, anything but a dielectric union. There have been many photos posted here of new steam installs with copper adapters straight into steel.  If it really bothers you, and you are acceptable at pipe fitting, put a brass nipple on each end of it where the cast is.

nicholas bonham-carter

cu or no

please describe what electrolysis has been evident.

if it is below the waterline, copper is approved, with a brass fitting separating it from the iron.--nbc

sooner302

Electrolysis

The electrolysis is evident,from the condition of the inside of the copper.The pitting,im guessing is the result of this.

nicholas bonham-carter

electrolysis

usually the iron portion of mixed metal piping suffers pitting, so maybe your pitted copper pipe is the result of something else. were any chemicals added to the boiler water?--nbc

sooner302

Electrolysis

There is evidence of pitting in the black iron,so much so that it has pin holes.This pipe went into a 90 at the botom of a riser. I dont know if anything has been added to the water,but i really doubt it.

nicholas bonham-carter

pin-holes in returns

now i am not sure where the deterioration is. is it the iron pipes, next to the copper, or both?

below the water-line, copper should be fairly long-lived, but  iron pipe will last quite a while as well. lack of main line [not rad] venting, coupled with high pressure, can cause the formation of carbonic acid in the returns, with subsequent "condensate grooving" on the bottom of the pipe. is this where your pin holes are?

plastic is a no-no, especially if the pressure is high enough to blow some of the boiler water up into the returns, during steaming.--nbc

sooner302

electrolysis

The copper pipe is pitted but not enough to leak....Yet. The pin holes were in black iron,screwed to a 90 which goes to a riser.Looking in both pipes, it looks like someone used a center punch,and a hammer. The copper pipe is 4inches off the ground-and below the wate line. Hope this clears up any confusion.