Copper vs. black iron in steam system

Steamhead

which is often caused by lack of proper air vents on the steam mains. How long are the steam mains? What pipe size? Do they have vents near their ends, and if so what make & model?

I would stick with black steel for your dry returns, since there is a chance steam may enter them. The copper patch in the steam main should also be replaced with black. But copper is fine for the wet returns since they are filled with water.

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Unknown

Copper vs, black iron in steam systems

I've got a 1920's house with one-pipe steam heat. The black iron return pipes are getting pinhole leaks where the pipe sagged slightly on long runs and condesate pooled. I am ready to replace them, but would prefer to work with copper. If I use the proper connectors (to avoid electrolytic corrosion between copper and iron), is there any reason I can't use heavy-duty copper with good sweated joints instead of black iron? Also, is there a reliable treatment I can use to limit further rusting in the system? Thanks.

Steamhead

Are these returns

above the boiler water level, or below it?

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Unknown

Yes--

Thanks for the reply.

These are the "dry" return lines above the water level. I am concerned about the wet return, of course. If it pinholes, it would make a real mess. It's behind drywall. You make me think about a good point in addition to the copper vs. iron question: do these return lines corrode out at roughly the same speed? Should I bite the bullet and replace all my returns?

BTW, I did have a pinhole last year with a horizontal steam feed line, and the plumber replaced the 5 ft. section with 3" copper. So, he either thought copper was OK or he wanted to get the job done fast...

Terry

TGO_27

Have you

checked the PH level of your system water? Steam systems can go acidic and cause pin holes in the piping. This can also cause corrosion at the water line in the boiler.
Hope this helps

Bob_19

No

I wouldn't use cooper on the steam side at all. Copper on the return side should bs acceptable, though I would check for any local codes on the issue of cooper and steam systems with your AHJ.
Yes their are chemicals that can be used for the return lines, some of these will coat the lines to keep acids from doing any damage, and some will keep the PH in the Akly range, say around 8-10.

Tony Conner

Acidic Condensate...

...is caused by naturally occuring alkalinity in make-up water, that breaks down into carbon dioxide under boiler conditons. It gets carried out of the boiler with the steam, and dissolves in the condensate. It'll show up as a general wasting of the pipe wall at, and below, the condensate level normally in it. Oxygen corrosion will show up as pitting, very often at the water line - either in boilers sitting idle (but with water in them) for extended periods of time, or in water lines that are only partially full. You can also pit boilers to death by feeding them a steady diet of make-up water. The colder it is, the more dissolved oxygen it'll carry. The addition of heat, like in a boiler, just drives the pitting process nuts.

The appearance of the inside of the pipe (or boiler) will tell you what kind of corrosion you're dealing with. A certain level of oxygen corrosion is unavoidable in steam systems the cycle on and off all the time. The vents operate to suck air in, and break the vacuum as the system cycles off. That's just the way it has to be for things to work right mechanically. It should be very unusual to see corrosion from acidic condensate in a residential steam heating system. Both types of corrosion can be pretty much always traced back to one root cause - make-up water. Keep the system tight, minimize the amount of water added to the system, and most of the corrosion problems will just never happen.

I very much dislike copper in condensate service. I'd go with steel pipe. Copper all by itself won't cause any problems. However, something else going wrong - such as a lot of carry-over from the boiler, can trigger events that will strip copper off the pipe walls, and send it back with the condensate to a steel or iron boiler. That's bad news. You'll suffer pitting attack very much like oxygen corrosion, but it's caused by the copper and iron/steel setting up a galvanic cell in your boiler. It doesn't nearly always happen. Some systems have copper return lines in place for years with no problems at all. However, with copper piping, one half of the equation is in place - the table is set. Why would anyone do this? By the time labour and material for steel vs copper are added up, what have you saved? Not much, if anything.

George_10

treatment

As the above post mentioned pitting corrosion is caused by oxygen. Thinning of the pipe wall is caused by a low pH situation.

Typically, an oxygen scavenger is added to the boiler to consume the dissolved oxygen in the make-up water and protect from pitting corrosion in the boiler. An Amine is used to treat the steamline and condensate return lines to protect them from pipe loss. There are two basic types of treating amines. One is a floating amine, the other is a filming amine.

I would contact a reputable chemical company or a reputable water treatment company in your area and they should be able to assist you. If you cant find anybody, please feel free to email me and I will be happy to help.