So fresh water carrying O2 causes corrosion. How about a HOT WATER TANK feeder into the boiler?

Your water heater boils the water?

There is some thought that feeding a boiler with domestic hot water is helpful in this regard, but I'm not sure. I haven't tested at what temperature the oxygen is driven out of water.

I've been using distilled water for makeup water in my boiler (in addition to 8-way, a pH-booster) and I think my boiler might last 100 years as a result.

Edit: here's some data. I guess I will boil my water before I add it to my boiler now.

• Practical examples:
  • Heating tap water to warm (50–60 °C) noticeably reduces dissolved oxygen but not completely.
  • Bringing water to a rolling boil for a few minutes removes virtually all dissolved oxygen; this is why boiled water tastes flat and why deoxygenated water is used in some lab procedures requiring low O2.
• Short summary: dissolved oxygen gradually leaves as water is heated; boiling rapidly expels the remainder. At 1 atm, by the boiling point (~100 °C) the dissolved O2 concentration is essentially zero.

You are filling mostly with mostly nitrogen, their is approximately 20% O2 in H2O, 78% nitrogen.

The O2 will be consumed in days by the oxidation process of any ferrous metals, expansion tanks, pump bodies, etc. Rust never sleeps!

Unless additional O2 is entering somehow you should have "dead" O2 free water within a few days.

That being said, O2 has many ways to sneak in.

Mother nature hates all imbalances. If there is an O2 free condition, she will do everything to balance, so O2 goes into the system. The wall of plastic tube, even with an O2 barrier,

gaskets, seals, packings, etc.

Many installers add a hydronic conditioner which contains oxygen scavengers to handle small left over O2, or ongoing oxygen ingress.

An example of a large commercial deaeration device.

Rarely seen on residential systems.

@hot rod has it exactly right. All large commercial and industrial steam systems should have Deaerators with boiler feed pumps to return water to the boiler. Also , the water should be treated as necessary by someone that knows what he is doing. This will extend the life of the boiler and piping system and allow the boiler to operate efficiently.

You are filling mostly with mostly nitrogen, their is approximately 20% O2 in H2O, 78% nitrogen.

I think you are thinking of how much oxygen and nitrogen is in our air

Yes and the air that is within the water.

Amtrol talks about the air, O-2 and nitrogen component. They did studies on the amount of "air" in water that enters you building.

This Amtrol Handbook should be required reading for anyone in the hydronic business. So, so many problems could be avoid if hydronic folk read this book. It is one of my most used books.

Excellent explanations of p

umping away, air removal, sizing, compression vs hydro pneumatic tanks, troubleshooting, etc.

I think an online version is out there.

Read the book and we can have a discussion. I trust Amtrol did their homework on this topic.

If you have a well or private source I don't think O2 is being added.

Public water providers do all sorts of things to water that might effect hydronic water.

I've visited several of the water providers in my state, and got tours of the their treatment facilities. I did not see or hear of O2 being added? That would have perked up my ears being in the plumbing and heating business, and specializing in air removal. But we have fairly good quality, good tasting Rocky Mountain water :)

Maybe back east it is about masking taste from all the forever chemicals that have made their way into aquifers :)

The amount of air in the water depends on the source, various pumping and treatments it goes through, how it is stored before it comes out of your tap, etc.

I doubt there is a set number to any of these observations and questions.

I think most would agree corrosion in open or closed systems has to do with the O2 inside, regardless of how or when it enters.

The DIN 4726 standard, if you can find and download a copy of that, talks a lot about this also, in regards to diffusion through tube wall

@EzzyT and @clammy install a filter on their feed water lines for sure. I don't think I've seen anyone else do it.

I use distilled water

These are becoming very common for one or two time use for filling residential systems.

These will scrub out all the + and _ ions giving you pure water. This will result in a low ph. The ph buffers up quickly as the water touches the metals in the system. The actual gallons you get out depends on how bad the water going in is.

Many, myself included, like to add a hydronic condition to give you even more protection . If the fill water is aggressive the conditioner buffers that.

A Culligan person told me much of the "distilled" water on store shelves is actually DI or DM water, maybe RO.

DI and DM is just running through a media, happens almost immediately.

I used to buy DI water from Culligan, they filled my 55 barrels with a 1" hose, that is how fast there equipment worked.

True distilled water is boiled, turned to steam, condensed on a stainless steel plate, so slower and more expensive to produce. Home counter top distillers for example produce about 1 gallon every 4-6 hours, using electricity. 500- 1500W depending on the model. No issue if you have PV I suppose :)

Very little difference between DI deionized, RO reverse osmosis, and distilled water, for boiler filling.

Those machines at Walmart are a pretty good deal for water in 5 gallon containers. I looked behind one and it looks like RO, a tank and some polishing filters, maybe carbon.

If you want 55 gallons call some local water treatment companies, Culligan, etc.

effectively the only difference between deionized and distilled is that deionized still has carbon dioxide in it forming carbonic acid.

Thanks for this clarification, Matt. I must have mis-read something at some point and am grateful for the correction!

@hot_rod said:

True distilled water is boiled, turned to steam, condensed on a stainless steel plate, so slower and more expensive to produce.

Or it's collected for free from your basement dehumidifier like mine is!

we were told that the di water in high school chemistry lab was acidic because it still had C02 combined with it. Don't remember if I ever tested that but I thought you saw it in some steps of the analysis process.

well said Ed.

You would not believe how many homeowners I’ve met who were told by their installer to drain their boiler every two weeks to keep it clean. Or maybe you would believe it!