# Why Not Electronic Solder For Some Joints



## AllanJ (Nov 24, 2007)

Just for curiosity's sake ...

Why is electronic solder (60/40, lower melting point) not used for certain plumbing such as ball valves and water heater connections near dip tubes so as to reduce the chance of heat damage?

(No it won't melt in domestic hot water.)


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## jerryh3 (Dec 10, 2007)

I believe it's due to the lead content.


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## micromind (Mar 9, 2008)

Not only the lead, but electronic solder has a rosin core. The rosin is somewhat poisonous. It would be very hard to get it out of the inside of the pipes. 

Otherwise, it'd work just fine.

Rob


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## AllanJ (Nov 24, 2007)

Thanks.

Still not sure whether I might use some anyway.


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## brokenknee (Dec 13, 2008)

AllanJ said:


> Thanks.
> 
> Still not sure whether I might use some anyway.


I would strongly recommend against it. It is not code and you really do not want to put lead into your water supply.


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## Tom Struble (Dec 29, 2008)

then why ask if your goin to do it anyway?


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## John McCabe (Jan 31, 2009)

It works really good, very low melting point and protects hte fixture. everything is bad these days and a little rosin core never hurt nobody.


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## Tom Struble (Dec 29, 2008)

thats crazy

then why dont plumbers use it?


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## brokenknee (Dec 13, 2008)

It's not the rosin core, it is the lead in the solder. But what the heck who needs all those extra brain cells anyway? 

Seriously, do not expose yourself or your kids to lead, the dangers are well documented.

Scroll down to health effects in this article and see if you still want to put lead in your drinking water.

http://en.wikipedia.org/wiki/Lead


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## Nestor_Kelebay (Jun 17, 2008)

I think you have to differentiate between "Not recommended" and "Recommends not to".

Most likely electronics solder would work on plumbing pipes. But if no one has ever done the testing with electronic solder on copper pipes, then no one is going to say for certain that it's fine to use as a replacement. So, you're going to get the standard boiler plate from the authorities that it's "Not recommended", which is NOT the same thing as them recommending that you don't use it.

It'd prolly work fine, but no one's done the testing to confirm, so no one's gonna go out on a limb and say it's OK.


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## Tom Struble (Dec 29, 2008)

dont ya think if it was better or just fine it would be a common practice?
you know alot of plumbers using it or saying it probably just fine?



i think you got the pizza tip right on but i think your off base on this one


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## Nestor_Kelebay (Jun 17, 2008)

Actually, StrubleSiding, you're right. I did screw up in posting that last answer because it's only dawning on me now that there has to be a major difference between the acid in the core of electronics solder and the zinc chloride used in plumbing solders.

With plumbing, we have to remove the copper oxide film that forms on the pipe and fitting with sandpaper or a fitting brush before applying the flux. The job of the flux is largely to form an film that's impermeable to air over the bare copper while it's being heated to soldering temperatures. (It also helps the solder wet the bare copper metal, too.) 

Plumbing solder will also contain a compound called zinc chloride (ZnCl2). Zinc chloride breaks down metal oxides, especially at higher temperatures (like soldering temperatures). The purpose of adding zinc chloride to the flux is to dissolve any residual copper oxide film from the copper pipe or fitting surfaces that wasn't removed by sanding or brushing. (One website I read said that at elevated temperatures ZnCl2 reacts with water vapour in the air to form one zinc oxide (ZnO) molecule and two hydrochloric acid (HCl) molecules, and it was the HCl that dissolved the copper oxide.)

http://en.wikipedia.org/wiki/Zinc_chloride

With electronics, there's no removing the copper oxide film from the wires, and there's no separate fluxing. So, even if the copper wire does get pretty darn hot before soldering, so that a thick oxide film forms on it, the acid in the core of the solder dissolves that oxide film in order for the solder to bond with the bare copper metal in the wire.

That would tell me that the acid in electronics solder has to be very much stronger to dissolve all of the copper oxide that forms on the wires while they're being heated up to solder.

But, whether that stronger acid would be a potential health concern if used on copper water supply piping, or if the lower melting temperature of electronics solder would result in a weaker plumbing joint, or if something else entirely is the crux of the matter, I dunno.

But, based on the above, my guess that the reason that electronics solder isn't used for plumbing is because the acid in that solder is much stronger than the zinc chloride in plumbing solder.

It's just a guess, but it's my best guess.


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## brokenknee (Dec 13, 2008)

I really think the rosin core is immaterial. 60/40 solder is 60% lead (thus the lower melting point) and 40% tin. You do not want to put lead into your drinking supply.

It is not permitted by code, at least in MN.


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## Nestor_Kelebay (Jun 17, 2008)

Fine. I agree that you don't want lead in your drinking water.

But, why were there still distinct electronics and plumbing solders used prior to 1980 when 50/50 lead tin solder was still used for water supply piping? And, 50/50 lead tin solder is still allowed for use in closed systems, like hot water heating systems. 

So, we're still left with the question: Why not, then, solder a zone valve in with electronics solder?


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## brokenknee (Dec 13, 2008)

And I agree the acid in the electronics solder is probably stronger. I do know however someone that used it back when 50/50 was legal and to my knowledge the joints are still not leaking today. 

I was only trying to stress my point of the health hazards the op would subject his family to if he were to use it. When it comes to the safety of my family every thing else is secondary. 

To me it makes no difference if he uses it or not; I just wanted him to understand the dangers. He should also list it on the home disclosures when he sells his home so others will know.

I am sorry if I offended you in some way, I was not disagreeing with your point on the acid core. The OPs' question had to do with potable water, not a closed heating system.


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## Nestor_Kelebay (Jun 17, 2008)

No offense taken.

I realize the difference in lead content is important.
There's also probably a big difference in the acid.

But, quite frankly, I find that when I solder I tend to use more solder than necessary, and I'd prefer if plumbing solder came thinner so that it wouldn't be so easy to use too much of it.

I think I'd like to see someone making a plumbing solder that's maybe not as thin as electronics solder, but a lot thinner than the 1/8 inch diameter stuff we're forced to buy now. Something like about 3/32 maybe.


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## brokenknee (Dec 13, 2008)

but then they wouldn't be able to charge as much.


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