copper return lines on steam systems

Rodney Summers · January 2006

Well, lets look at the pros and cons...

Copper will survive carbolic acid in condensate better than steel and probably woun't leak as soon, unless its underground without the proper protection.

Copper woun't rust inside and clog with its own rust as steel does.

Soldered copper joints and pipe are nowhere as strong as steel and can be subjected to physical damage.

Copper definately calls for di-electric unions between it and steel according to some codes and good engineering practice, somthing we never do and in the field hardly ever causes any problems. I've never seen an electrolysis problem on a return line.

Any twisting caused by expansion will work toward doing in a soldered copper joint.

The quality of copper pipe lately is a little inconsistant, and some 5 year old pipe is developing pinholes. Ditto for steel pipe -- there's some junk out there.

Copper appears more vunerable to electrolysis caused by stray voltages -- say a house with a bad electric service ground.

Copper pipe need more support and hangers.

More profit in installing steel.

Labor? Obvious.

If someone came to me as an engineer for an opinion, I'd probably say "Steel is the perferred material but copper is an acceptable alternative," an opinion which is weighted heavily by tradition and custom.

What do you think?

Long Beach Ed

Paul_11 · January 2006

copper return lines on steam systems

Does anyone have written information on why copper is better than black steel for return lines?
Can you help out with any books, Dan?

I have used copper for all of my condensate return lines on steam systems for many years with no problems. I always switch from black steel to copper below the water line.
On a job we are currently doing a customer has questioned the quality of my work saying that electrolysis will attack the joints. He is a scientist. He says black steel would be a better job.
I have tried to explain the physics of all this, but to no avail. I told him that electrolysis could occur if the system had leaks, and a lot of fresh water was being added. In that case the boiler itself would be a bigger concern for me and not the return lines. If the system had leaks, the leaks should be fixed. If he didn't have leaks the boiler would burn off the oxygen. By the time the steam became condensate and got back to the return line it would have very little oxygen in it. Since you need oxygen to have electrolysis, you don't have to worry about the return lines.
I told him if he wanted black steel, which is a more work, but less quality, I would submit an extra. He said he would pay it, but I really don't want to do a job of less quality.

He did ask me for some documentation on what I was saying, which is the reason for this email.
Does anyone have written information on why copper is better than black steel for return lines?
Can you help out with any books, Dan?

Respectfully,

Paul B. Shay
pshay@arealgoodplumber.com
LMP 1307
LMFS 654B
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Rodney Summers · January 2006

Sorry, Paul

... I agree with your customer.

We use steel, but have seen excellent results with copper also.

I'm interested in seeing what others have to say. I may well be wrong.

Long Beach Ed

Phil_6 · January 2006

copper

I almost always use steel if possible but have used copper a few times with no bad results that I know of. I wouldn't call steel 'less quality' I would call it an upgrade.

Steve Garson_2 · January 2006

Electrolysis does not need oxygen.

Galvanic corrosion (electrolysis) requires the presence of two different metals, a conductive (metallic) metallic path between them, and an ionic path (water or moisture connecting the two metals). Copper and steel offer this combination, so electrolysis can occur. Generally the best way to stop it is to use plastic(hose, dielectric unions, spacers) in some way to break the conductive path between the two metals.

Mike Cascio · January 2006

That being said, with something like a dielectric union on both ends, wouldnt copper be less suseptable to damage underground than steel?

Michael J. Cascio

Darin in Michigan · January 2006

The guru

The guru at my old shop used to say the copper would twist in the fittings causing wear and eventual leakage at the joints.

bob young · January 2006

copper returns

I agree with you 100 % Paul. been using copper for returns since 1972 and not one problem and still got the same customers. the ones that are alive anyway. and if i am in a good mood i use L instead the usual M. ALWAYS SOLDERED WITH 95-5 OF COURSE. in the old days i brazed them . overkill. bob young n.y.c. lic. plbr. # 685

RonSBC · January 2006

New guy here for the most part so go easy on me, please.

I prefer steel, its a superior metal for one. A soldered joint would be a no-no in my book, but a brazed copper joint would be fine, and have superior integrity. Steel would be more susseptible to water chemistry problems but there is alot of steel to go through to reach the atmosphere. Steel is more classy than copper for steam work it requires more skill and looks better in my book. Also concider the co-efficient of expansion of the two metals, copper would start to develop leaks after years of on-off, hot cold, but not at the pipes, more than likely at the fittings that would be stressed. And i personally would never use less than "K" pipe copper for steam anything.

Electrolosys, instead of di-electric fittings try using an intermediate metal. there is a chart that shows in order metals comonly used in piping. copper and steel, use brass as the intermediary metal and you will have a break in the electrolitic effect. that dos'nt stop the corrosion it mearly slows it, this is true of all di-electric fittings (except those that truely seperate via non-conductive materials) as the nature of the metals differences are less severe with a brass intermidiary.

As often as possible and only because i have a good threader i change the cheaper installed copper pipe for steel. Thats my take, copper is good to keep the initial cost of the job low, not becuase its better for steam.

copper return lines on steam systems

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