New Boiler, Dirty Water

Larry in Elkins Park_4

I have a question regarding dirty water in my new boiler. The system seems to have been adequately cleaned, and water is not oily. Steam and heat are fine. But after heating for a week there is a nasty chocolaty build-up in the sight glass, draining the sight glass and opening up the tap under the lower cock, it's really filthy. Since install I've twice drained and recleaned the system, takes about a week for this to come back.
Now--I suspect this is because of my copper mains. I know I will be excoriated for this, but replacing 110 feet of mains of varying size (44' is 3 inch) that had been prior replacement before me for failed steel/iron is not in the cards at this point. Header is new black pipe, as is first 4 feet of supply riser, but equalizer and Hartford loop are also the old copper that was there. Risers and some smaller main pipe are steel/iron.
System runs fine and is over an hour before pressure builds. Then it generally runs 5 minutes on to get to the cut-off at just about 2 psi, 5 minutes off to drop. Main is only vented by a Hoffman 75, a Gorton 2 can't go in that location. An oddity of the layout is that what appears to be 45 feet of dry return isn't, as at that point there is one last riser that feeds to a second floor radiator (and actually closer to the the boiler, BTW--only about 3 feet of wet return after this all goes below the water line). The main vent is at the penultimate feed, although this does not seem to slow the heat to that last rad.

So the question is--do I have a serious problem with the what I am guessing is copper residue that keeps appearing. Which is more harmful--that or purging the system every week or two? Does anyone consider how this ultimately runs as short cycling? And do I really need to get more venting in, since I am heating okay? Let's try to keep the roasting of me for the copper to a minumm :-)

kevin coppinger_15

new boilers...

bring out all the old stuff from pipes. It may take a number of weeks to "clear" it of junk. The flushing will not hurt the boiler...we are talking a flush every day or so....hurt would be every day for months.
Add a couple of tees to add another #75 or another Gorton #1. 1 # 75 is too small..are you sure a #2 won't fit? You don't have to come off the top...the side works too.