Brown marks on Wirsbo HePex

Kestrel

Hello again.

As I've been finishing the basement framing, I've been seeing several places where the 3/8" pex is discolored.

When I first got the system up an running a few months ago, I noted that the tubing was turning uniformly brown, most intense near the supply manifold, and fading out over the length of the runs, nearing normal at the return manifold.

I though it was perhaps copper, or copper/flux residue that was reduced (as opposed to oxidized green - I had a fair amount of green and white flakey/pebbley debris in various faucet aerators after I finished work on soldering some domestic supply lines).



Now however I'm seeing in a couple of different locations more discreet, intense brown marks on the pex, looks like on the inside, and overlaying, on the outside surface, are what look like abrasions - very small, very fine fibery/flaking stuff.  The pic is from two spots very near the supply manifold, and I've found another in a joist bay, some distance away.



I'm sure the tubing got a bit abraded being pulled through holes in the joists - but I didn't see any real abrasions at the time.  The exact correspondence between the scraped outer surface and the inner brown discoloration has me worried, but I have no idea what's going on.



Any thoughts?

Thanks in advance - I'm getting near sealing up the joist bays (basement remodel - teenager mancave) and I'm worried I'll be covering up a serious problem.

Mark Eatherton

Oxygen barrier compromised...

Any where on the tubing that the EVOH barrier has been scratched or otherwise removed, oxygen will move through that section of the pipe. You have (I assume) ferrous components within the system (pumps, nipples, air separators, etc) and there are free metal oxides floating through the system. Whenever they find the oxygen source, they attach themselves there, and what you are seeing is the net result, oxidation.



I've seen much worse, with no appreciable system degradation. It is important to maintain the proper system fluid pH to diminish the amount of oxidation that can occur in the system, but I wouldn't lose any sleep over it. There are plenty of other places for oxygen to make it freely into the system (diaphragms, rubber gaskets, etc.



Carry on....



ME

ColoradoDave

Normal

We've had old cast iron boilers with PolyB tubing (no oxygen barrier). 

On boiler replacements going in a high efficiency stainless steel heat exchanger, we put in all copper & brass, pumps included.  After flushing the system with a charging pump and tsp before the boiler went up on the wall, we thought we had it flushed clean and we STILL get the same discoloration. 

I wouldn't worry about it, just check the pH of the system water every couple of years.

Kestrel

sigh of relief

thanks guys - that's very reassuring for this newbie DIYer.