Oxygen dissociation

Nope! My whole house is plumbed with pex, no issues..

snuffy wrote: ↑

Tue. Dec. 29, 2020 7:23 pm

Ahh this thread helps me understand a problem we have with a renovation project in our basement. The contractor replaced about 15' of 1/2" copper pipe with PEX (red and blue) to connect to a utility sink. Prior to the reno the water was always clean. Post reno the the water after two seconds turns charcoal color for about 8 seconds which would corelate to the amount of water in the PEX pipe and then turns clear. I wonder if this oxygen dissociation is causing the discoloration in the PEX.

Any ideas if this is the possible cause?

I don't think so. Lots of pex in my house, and I have never seen anything like you described.

All plastics are gas permeable to some measure, including oxygen barrier plastics. Copper is not gas permeable.

If a plastic existed which did not permit the inflow of oxygen, beer intended for longer term storage would be sold in plastic bottles. No such bottle exists, so its cans or glass bottles. The plastic stadium beer bottles are intended for nominally immediate consumption. Even the properly sealed 'crown' cap of a glass beer bottle is detrimentally gas permeable. That leaves only cans for truly long term stability.

snuffy wrote: ↑

Tue. Dec. 29, 2020 7:23 pm

Ahh this thread helps me understand a problem we have with a renovation project in our basement. The contractor replaced about 15' of 1/2" copper pipe with PEX (red and blue) to connect to a utility sink. Prior to the reno the water was always clean. Post reno the the water after two seconds turns charcoal color for about 8 seconds which would corelate to the amount of water in the PEX pipe and then turns clear. I wonder if this oxygen dissociation is causing the discoloration in the PEX.

Any ideas if this is the possible cause?

I would be more suspicious of the pex fittings than the pex itself.

I'm confused by the term 'dissociation'. This term is used (in the case of the oxygen molecule) to describe the energy level at which O2 dissociates into two individual 'O' atom/ions. A boiler is never anywhere near dissociating molecules of oxygen. There must be a more appropriate term to describe the phenomenon being discussed. Oxygen "ingress" perhaps. ???

Isn't this why you should treat your boiler with cryotek or whatever. Not only antifreeze but has a rust inhibitor in it. I dont use it and I dont drain my boiler. Im not all that worried as water is usually pretty clean looking. The inside of the water jacket has a black film on it not rusty orange.

Water entrains oxygen between freezing and 153°. It's know as dissolved oxygen. It is what keeps plants and fish alive under water. It absorbs it naturally however I can't explain the process.

Ah ok.. meaning between freezing and 153* it can absorb free oxygen from the atmosphere.

Exactly, it's what it does. Just above freezing and at 153° it drives the oxygen out of it. Or "dissassocites" from it. At that time it will be a gas in the system and be expelled by the scoop and vents.

I would have to speculate though that free oxygen from the atmosphere to penetrate into a sealed boiler system would be extremely slow. I also assume that the destruction of the boiler that Larry brought up was from condensation, which is something different.

Yes, two different things...

Disassociation is for NEW water filled fresh into interior or wet side of the steel vessel.
In light of NEW water fill not ever reaching ample disassociation temp of 160* for prolonged period may need a chemical assist to accomplish oxygen depletion.

And other is acidic condensation on the exterior or dry side of the steel vessel in the exhaust path. As was said, ALWAYS Stay above 140*.

BTW: Even with burning DRY coal there will still be enough moisture available to condense at too low of temperature

I have a handfed boiler. Found it hard to keep it above 140 at all times! Without being there constantly feeding it, it’s just a matter of time throughout the day where it falls below on temps. So with that said, yes there is a real scientific truth to oxygen going into a system running at low temps. It may very well last a long time either way!

I'm running well under 140 and the only time I see any condensation is when I put new coal in. but only on the sides where the firebox door opening goes through the water jacket. After the new coal gets burning it's dry as could be through the entire firebox. I know for sure, cause I've stuck my hand in there and felt around, even above the baffle. Not arguing by any means, I'm guessing my system overall setup/design has something to do with that.

Still concerned about inside the water jacket. As it stands now with no solid proof of oxygen dissociation being a real threat for my system. I will be inspecting the water jacket every year. If I see evidence I will take other avenues.

Condensation is not oxygenated water inside the pressure vessel. We're talking about two very different things now.

For the condensation I was referring to inside the fire box. I'm not concerned about that at the moment, however I will still continue to monitor it.