After installing durapex as a partial run to a radiator in my 90 year old house, I come to find that I should have used pex with a barrier instead.   I found out  that durapex allows oxygen to enter the water from outside the pipe, and thus will cause corrosion of a cast iron boiler in a closed loop system.

First off, I had to search pretty hard to pick up this piece of info after the fact, as both durapex and pex are recommended for hot water heating systems.  You would think that they would label durapex with DO NOT USE WITH CAST IRON, but they (the mfrs) don’t.  This info was in fine print on a random piece of literature.

So I have about 60′ of 3/4″ durapex (30′ supply, 30′ return) behind finished drywall.  Is this something I need to lose sleep over, as much of the pipe in my system and all of my old radiators are cast iron.  I’m assuming that my weil-mcclean boiler and pump are, also.  I was thinking to add some rust preventative additive sold at the local plumbing supply house to my system before starting it up for the year.

I called a tech fella at CPI, the company that makes the durapex I used.  Nice guy.  He said that it does allow oxygen to enter the system, but had no data available on the extent of the transmission, etc.  They did not have any tests in progress, either.  He couldn’t say how rapidly the transmitted oxygen would corrode a cast iron boiler either.  But that it would corrode the cast iron eventually.

Then again, my boiler will die on its own “eventually”‘ too.

Is this issue a fact of concern, or is the oxygen factor of negligible proportion (esp. with a minmal number of lf).

Your comments are appreciated.

DIA