That Pesky O₂ Molecule – How Oxygen Finds Its Way Back Into a Steam Boiler

An observation about where oxygen does its real damage:

You are right that oxygen enters cold water and we do of course see returns (usually at the boiler) rot out pretty quick.

However, where do the boilers always fail? At the top of the section, every single time. How is that possible? There's no water up there, there's only air and steam, right?

You also said in your video correctly that the oxygen is forced out of the water as the water is heated. But I would ask "where does that oxygen go?" It is released into the steam chest, or the upper part of each section, where it is free to attack the cast iron. This is why I think it doesn't matter when you heat the water you add to the boiler—regardless that oxygen is going to be freed to attack the boiler.

So in my mind, the best way to keep your boiler from seeing premature rotting death is to use makeup water that was recently boiled, and to use a product such as 8-Way that has oxygen scavenging capability as well as the known corrosion-reducing pH booster chemicals.

Thank you for your video!

@ethicalpaul @hot_rod

This is one of my main concerns with my steam boiler. My water make up is from the cold water supply. We've only been in our house 2 seasons so I was only able to insulate some of the mains and condensate returns that were accessible in the basement. Another problem is I don't think I have an easily accessible port to add chemicals. The only vertical piping is the PTR valve and it's soldered in place.

1. Where would you recommend I add my treatment chemicals?
2. Do you recommend placing an inexpensive small tankless hot water unit & O2 separator inline with my water make up? I would prefer not to pipe off the hot water heater.

Thanks!

Just cut out the soldered pipe, connected to the relief valve. Reinstall with threaded or compression fittings and piping

Could we consider rot above the water line as a victim of O2?

What are folks view on a small carbon block filter on the feed water to remove chlorine and light solids… not worth the bother, no point?

@ethicalpaul hello from MI! Thank you both for the info. I am manually adding make up water around every 7 to 10 days when I hit low water cut off and the house gets cold, so I don't think your suggestion is the correct solution for me. I do appreciate your dedication 🫡. I have looked at every single pipe and wall in my house and I would swear on my life there are no leaks. In terms of ease and function, I think @STEAM DOCTOR's suggestion is the one I feel most comfortable with completing myself.

Is your main concern with an external heater/bubbler that the potential for leaks increases with more connections?

Yes I have noticed the same thing from a distance of this forum @STEAM DOCTOR that all holes seem to always be at the top of the sections.

And yet the other major rot point always seems to be where the wet return hits the boiler, so something interesting happens there as well.

@Day_Tripper that is a lot more water than I like to see being added. Look for leaks of steam or water, especially the vents. There is also the possibility that your boiler has a hole in it as seen in the above picture (but probably smaller). I want to see less than 1" of drop in the gauge glass every month or so during the heating season. Using as much water as you are using will reduce the lifespan of your boiler. Of course if it already has a hole in it that concern is in the past.

Is your main concern with an external heater/bubbler that the potential for leaks increases with more connections?

No, just that it's a lot of hassle for minimal benefit

if your vents are letting steam out, that could be the whole leak.

the easiest way to test the boiler is to overfill it to the header and see if water starts raining down to the floor under the boiler

You are in a difficult situation with that removed radiation.

But you are exacerbating it with that 5 degree setback at night. I recommend stop doing that and see if the downstairs is able to stay comfortable.

If the upstairs gets too hot for your comfort at night, try covering one or more radiators with blankets until you are comfortable, but keep in mind doing so is similar to removing radiation and may make your system cycle more.

Cycling more isn't a big deal for gas, but could be more problematic for oil.

@ethicalpaul Thanks again. I'm going to put that thermostat on a permanent 72 deg hold. We have radiator covers with top hinges that I can close or prop open a bit with plywood to increase/decrease air convection. I'll keep the upstairs covers down and the 1st floor open. Thanks again.

No, I don’t think 8-way protects the mains. I have thought about carryover helping but given that even a sagging, rusting main lasts 100 years, it hardly seems worth it to consider.

These pictures show corrosion on upstream end better. I'd estimate 1/2 way through penetration at the worst spots. Uneven corrosion must be due to localized differences in alloy composition, and once the pitting corrosion starts a self perpetuating small pool of water exists. Definitely a different situation from boiler corrosion with treated water and mostly de-aerated water and "maybe" some protective effect from scale buildup.

this question would be better as its own discussion thread.

But I would suspect carryover is occurring

Carryover is when the boiler throws water up into the near boiler piping, and/or the header, and possibly as far as up to the radiators where it can potentially fill them and shoot water out of the vents, although that would be a pretty extreme case.

The easiest way to determine it's happening is to observe the gauge glass while this is happening. Does the level dive to the bottom of the glass?

That's right at my personal limit…with that drop it's hard to know if it's carrying over or not, but in any case it's not a crazy amount.

Is the vent still blasting? Also define "blasting"—different people have different ideas of how much water is a lot

And leaks add up fast. For about 10 years I had a leaking radiator. It leaked between two sections but leaked at the top of the radiator so only steam would come out, no water or drips. I considered it "minor".

It would not be visible to the naked eye but you could hear it if you got close to it when the boiler was operating under pressure, say 1-2psi. My boiler is oversized so it does cycle on pressure.

Blowdowns aside I was adding water weekly during the dead of winter. Probably about 1-2" per week on the site glass when it was really cold.

I removed the section of the radiator that was causing the leak and put the radiator back together. No more leak and I now add water maybe twice a year, not including what is lost during my occasional blowdown.

That "little", barely noticeable leak was probably losing a gallon or two of water per week during the coldest part of the year.