Oxygen ingress, fact or fiction?
A local job, rubber tube staple up, requires 160F SWT at design. The system has gone through 3 or 4 boilers since being installed early 1990's. Many expansion tank failures according to the property managers. My experience is the thinnest metal components fail first, some within months.
A contractor I know locally was the most recent to work on this system. A new boiler and hydro sep was installed, 18 months later a leak developed in the thick steel separator tube.
Here is a look inside. The system has an Axiom fill tank, no leaks, no fill water added.
I had a folder documanting failed components on non barrier systems, expansion tanks, steel radiant manifolds, pinholes on steel fittings, etc. I lost track of it on my last computer switch.
I worked on non barrier systems since the late 1980's Solar/ RadiantRoll, PB, Heatway, and still as we speak non barrier pex systems.
Its pretty clear the O2 ingress is a reality, and higher temperature systems fail sooner than low, radiant temperature applications.
trainer for Caleffi NA
Living the hydronic dream
Comments
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That's some aggressive water! Was it ever tested/ treated?
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We've seen it a bunch of times as well. Last time was on a no heat call at a new customer. As soon as I saw the "black rubber" tubing I new it was going to be trouble. It was 4pm on a Friday and he mentioned there was a small leak he needed repaired. When I looked at the near boiler piping, every fitting looked like it was about to crumble.
In a pinch I delicately replaced the expansion tank, a few pieces of rotted steel pipe and the iron circulator. Afterwards I slowly filled the system and started the gas fired cast iron boiler. As the began to warm up I noticed two of the four zones appeared to have no flow. The owner casually mentioned this is a long term problem that is getting progressively worse.
In the end, I surmised that the cold zones were actually clogged with debris and I could not clear them with city water pressure (about fifty psi). I wrote a proposal and never heard back from him. It would not surprise me to find the boiler and radiant tbung still in place. I amost forgot the Entran? tubing was used for the entire radiant first floor (half slab half above finished basment) and the hwbb zones upstairs (ran through the slab also).
On a side note, it appears that your home labratory serves as the Caleffi destructive testing site as well? I'm guessing with almost 800 inches of snow your not able to get out these days (lol).
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I'm no scientist, but I think its very clear that is the case. Mad
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I do find it odd that I go to some jobs with entran and some with onix, and they are still working and well. Some are 20+ years in and still rolling. Then I go to some that are less then 10 years old and the expansion tank goes bad every year, and the system is slowing???
Tom
Montpelier Vt
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I know Tom...definitely enigmatic but so are alot of things in heating that leave us scratching our heads. The oxygen permeation through the "naked" tubing seems like the same principle as "high pressure goes to low pressure....and Hot goes to cold."
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I suspect the rust "grows" rapidly when the system is run at higher temperatures
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DIN Standard 4726 addresses this. I would have to do some digging to find some of the Wirsbo videos that we made of the testing process and the results but it is amazing how fast issues occur. Nature hates an inbalance.
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It was odd how the tube failed and became "glass brittle" in some sections, while other sections stayed pliable.
I'm not sure how consistent you can keep the O2 barrier on a tube that is extruded that way?
With Pex the barrier is added on the exterior of rhe tube.
The current version of Rubber tube, Onix has and aluminum layer wrapped around, that should be 100% O2 barrier. Yet we still ocassionally see sludge systems. Could enough O2 get in around the fittings.
We rarely if ever see barrier Pex with O2 ingress issues?Makes you wonder about the barrier free PP tube🧐
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream1 -
Comparing rubber tube to non-barrier pex is no different than comparing a dirt floor to a reinforced concrete slab. They both do the same job, but with extremely differing effects. I cut into maybe 10-15 non-barrier pex systems annually, some fairly new and some older than me. Not once have I seen any evidence of troublesome o2 ingress where there wasn't also oxygenated site makeup water being added. While I would never install non-barrier tube in a hydronic system for any reason, it's not nearly as detrimental as some very influential forms make it out to be. I've been asking for upwards of 10 years for anybody to show me some evidence of problematic o2 ingress in a leak-free NB pex system, and have gotten only crickets. Maybe this post will change that for me?
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Which begs the question why wouldn't you install non barrier tube?
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
Because it doesn't have an oxygen barrier and I do things properly when the opportunity is given. Any ingress is worse than none, right? This whole "I know everything because I read it in a book" attitude is getting pretty tired. Almost as tired as the passive-aggressive shots at anybody who challenges these "facts" that nobody has previously had the experience and willingness to challenge. This trade came to be what it is today by trial and error along with people willing to put in the time and effort to write the book. The book was written with what was known at the time of writing- adaptations are necessary sometimes as things are always evolving. Smugly responding to new data with "nuh-uh", is no different than arguing with fuel injection when it came out. Once we stop willing to learn and adapt, we fall as a trade and as a people. Learning is good for everybody.
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By all means, challenge the status quo, but please present this "new data" that is being "smugly responded" to, rahter than just act like everyone should believe you because you said so. Because so far it's just empty claims, and one picture of an expansion tank that didn't fail, where the data on o2 ingress is pretty extensive, and also backed up from field research and contractors working on the systems every day.
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Basically this discussion goes back to 1974.
And it was not just trial and error on the fieldThis was a good read for me
Article: The Oxygen Diffusion Debate - DefusedNotably: "The general rule is: if the total amount of steel
surfaces are 5 times larger than the plastic pipe surfaces,
tubing without barrier can be utilized."There's a lot that leads up to that and more afterwards so wouldn't take that at face value. Just mentioning it as it's possible a system with a huge combined steel surface area + non barrier may not see the quick failures of expansion tanks as others where it is the only ferrous equipment.
The most widely used oxygen barrier is EVOH on the exterior of pex. But that only minimizes the ingress of O2, not completely block it. So the amount of tubing, temperature, and environment affects all results.
I mention environment because pex is not the first/main use of EVOH (food plastic industry). EVOH has great oxygen barrier properties but it loses a lot of it's barrier properties in high humidity. This is important and a reason why many manufacturers opt for moisture resistant protective layer on top of EVOH calling it 4 or 5 layer pex depending on if they count the adhesive layer.
There is a major manufacturer of EVOH barrier pex that makes it without this protective layer. And is one that relabels for many other brands. Rifeng. Supplyhouse (bluefin), Pexuniverse (everhot), Riifo, Zurn, Watts, and more. Not that big of a deal in most cases, but something to note if the outer layer of pex will ever be in contact with moisture. And to be careful dragging pex on the ground.
They do make pex-al-pex and evoh pex with a protective layer, but if you were comparing pex tubing pricing online and they are both pex-b or pex-a oxygen barrier, there are such differences that are not explicitly stated.
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Notably: "The general rule is: if the total amount of steel
surfaces are 5 times larger than the plastic pipe surfaces,
tubing without barrier can be utilized."Basically if you use a steel boiler, steel expansion tank, ferrous circulators, connected to the 1500' pex you are safe? Is that a common installation today?
Most residential or shop systems are much larger?"Amount Of Tubing 3" seems more common, attached below.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
It was picked out as a reasonable explanation as to why some of the systems GroundUp has encountered with non-barrier pex did not have these specific failures as of yet. Not that you should be installing non-barrier pex because it's potentially ok.
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I've seen some polybutylene systems with corrosion issues, a contractor was installing them in the late 80's in my area. On one of them the steel piping was severely corroded. The others were full of sludge. It's hard to know the make-up water history on them though. I've only seen a couple non-barrier pex projects, none of them looked like the polybutylene ones, but they're not anywhere near as old.
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I wonder if water quality (low ph) with higher temps accelerates the destruction that we are seeing.
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with glycol systems low ph, indicating the inhibitor has depleted, does cause the fluid to become more aggressive. It is a know failure in solar thermal systems with over heated glycol.
I don't know of many areas where the ground or treated public water has low ph? Acid rain was a thing in some rust belt areas.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
How ironic that you mention acting like everyone should believe you just because you said so. Isn't that exactly what Hot Rod does with almost everything questionable? I have been asking for proof of non-barrier pex causing corrosion issues for over a decade and have yet to receive any. I asked again here and got nothing. On the contrary, I provided photographic evidence of one particular NB system with no corrosion after 24 years. Now it's somebody else's turn to provide some evidence to their claim. This is kind of like the dielectric fittings at dissimilar metals transitions. Everybody says you need them, but nobody can provide an exmaple of electrolysis or galvanic corrosion on one such joint in a leak-free closed loop hydronic system. This corrosion also comes from oxygen ingress, which is not present in such a system. All I want to see is proof of detrimental o2 ingress through the pex tubing itself.
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you don't believe the science, stated in the Roth white sheet, Mr Pex aka Tomas Lenman warned us, as did Joe Fredrick back when non barrier rubber tube was introduced.
You don't trust manufacturers, or pics of failed product shown here for 20 years. The Sep pic I showed, numerous pic KevinC has shown over the years. Ask heatmeister his experience with O2 ingress.
Everything is a conspiracy theory in your world?
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream
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Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0
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