How much flux is too much flux ? And some more ??

mowersNovember 20, 2006

I saw on This Old House, a cross section of copper pipe that failed due to too much flux, and it created errosion downstream (not sure if errosion is the correct term). I am a do it yourselfer, but now it has me thinking, did I overflux thinking more is better? Why does the flux not just wash away? Does it permanently "stick to the copper?"

While I am on the subject, for 1/2 pipe, how much solder do you add to the joint, I find myself adding too much for fear of not soldering completely and find it often pools at the bottom of the joint. Do I just tap it once? Can you actually over solder a joint filling the inside of the pipe, or does it just not accept anymore and you are basically wasting flux to the point it drips off the joint?

And while I am on the subject, what solder should I use, there is a "red" and "green" labelled roll at Home says silver and the other a tin mixture? Why two types? The store rep said the silver is better and more expensive, but they both do the same thing?

Thank you for reporting this comment. Undo

If you're soldering a 1/2" pipe, use 1/2" length of solder, 3/4 = 3/4, etc.

Just wipe off the excess flux and you'll be OK.

    Bookmark   November 20, 2006 at 7:39PM
Thank you for reporting this comment. Undo

I once saw on the news that a young man died of drinking too much water during a college fraternity hazing incident. Does this mean that we should all immediately stop drinking water?

Flux is properly applied to the raw male end of the pipe, but never put inside the female opening of the fitting. Due to the close tolerances between the OD of the pipe and the ID of the fitting even if we put excess flux on the pipe the excess is simply pushed out of the joint as we insert the pipe.

Flux is an acid base and when excess flux is left on the exterior of the pipe after soldering it will promote premature corrosion of the pipe wall. Properly when soldering all joints should be immediately wiped with a clean damp lint free rag to remove the excess solder while the pipe is still warm. (Although the term is seldomly used today this explains why many old timers still refer to solder joints as "Wiped Joints").

Generally when novices are having difficulty consistantly making solder joints the begin a regimen of changing from one torch to another, changing from propane to MAPP gas, changing type, consistancy and volume of flux all of which produces basically the same results.

The one thing which we cannot emphasize enough, if there is an true secret to soldering it is CLEAN THE PIPE AND FITTINGS.

The methods that you use to clean the pipe and handle it after cleaning will have more effect on the quality of the solder joint than all the other conditions combined.

First of all, never be lulled into the notion that you have brand new pipe and fittings therefore they won't need cleaning. No matter how brite the copper may appear in the package the surface of that copper has a slight oxydized tarnish, in fact, if you clean fittings then let them set overnight before you get a chance to use them it is best to clean them again. Over the years I have adopted a personal policy that if it has been more than four hours since the fitting was cleaned I clean it again. Cleaning a fitting is much too quick and easy to risk the time lost to a bad solder joint.

The outside of the pipe wall should be cleaned with a fine abrasive emery cloth or a stainless steel wire brush pipe cleaning tool. You can find a precut 2" x 50' roll of emery cloth commonly called a "Plumbers Roll" at any local hardware store. You will find both a cloth back type and aa Open weave "Sand screen" type. The cloth back type is a bit cheaper but in use the abrasive loads up quickly. You will find that although the open weave type costs a bit more in the long run a roll of open weave will outlast two or three rolls of cloth back emery.

To use the emery tear off a piece about 8" to 10" long then loop it over the end of the pipe and alternately pulls the ends back and forth like a shoe shine rag until the pipe is bright and shiny. Absolutely do not touch the cleaned surface with your finger as dirt, debris or even the oils in your skin can contaminate the surface and effect soldering. If you must lay the cleaned pipe down always lay it over a block or something that will keep the cleaned surface away from the floor. Do not stand it on end on the floor or leaned against a wall as that can contaminate the cleaned surface.

The interior of the fittings should be cleaned with a fitting brush. You can find cheap wire framed fitting brushes in any hardware store. I prefer to buy two or three of the cheap ones that way if you drop one in the dirt you can quickly grab another rather than risk contaminating the fitting. (here is another tip, if you have a lot of fittings of the same size you can cut the wire loop handle off a fitting brush then chuck the brush in a cordless drill and power clean a whole bag of fittings in a few minutes).

Flux should be applied only with a flux brush. You can find very inexpensive disposable "acid brushes" in the plumbing department of your local hardware store in the same area as solder and flux. Typically they cost about $.10 so grab a bunch. If you drop one, dispose of it and get another.

Now to try to answer your questions about solder.

Solder is manufactured to the ASTM (American Society of Testing & Materials) standard ASTM-B32

ASTM B-32 grade Sn 63 solder is the standard 50/50 allow of lead and tin. (This type may not be used for potable water applications).

ASTM B-32 grade SB5 (Lead Free) is an 95/5% alloy of tin & copper.

ASTM B-32 grade E and grade HB is a Lead Free alloy of 95% tin with a trace of silver from .4% to 5%.

The inclusion of silver in the allow slightly reduces the melting point and is purported to flow better but in reality the slight reduction in melting temperature is only 10degF (450degF to 440degF.) and in practice it is hardly worth mentioning. The inclusion of silver does somewhat vary the hardness of the solder joint but here again even the weakest of the lead free solders has a tensile strength greater than the actual strength of the copper pipe wall.

    Bookmark   November 20, 2006 at 8:06PM
Thank you for reporting this comment. Undo

Wow, nice description. I guess I am doing it wrong...I put flux on both the male and female end. Oh well, never to late to learn.

    Bookmark   November 20, 2006 at 8:58PM
Thank you for reporting this comment. Undo

I put flux on both fittings as well. After a couple of cold joints, I figure I do not want to risk it. I have had joints that I cleaned and fluxed but just won't take the solder.

    Bookmark   November 20, 2006 at 9:28PM
Thank you for reporting this comment. Undo

Flux should never be applied to the inside of a fitting. When the pipe is inserted that flux is pushed into the pipe and into the water path. Apply the flux to the male end only, then after fitting the male end into the female fitting when possible you should rotate the pipe a bit to insure the flux is spread evenly.

    Bookmark   November 20, 2006 at 10:02PM
Thank you for reporting this comment. Undo

Well, heck. I am a double-fluxer myself.

You see? My understanding of flux is that it is a chemical cleaner. That is, it is an acidic reactant, which makes the topical surfaces of a sweat joint appear almost perfectly clean. Or, to say it another way, unspoiled; or un-oxidized.

(Oxidation, while usually associated with oxygen, is actually an electrochemical reaction which can occur disassociated from oxygen, yet electronically equivalent.)

Anyhow, as a practical matter, what is sauce for goose is sauce for the gander. (That is a quote, actually. I wish I had thought of it myself.) Or, in this case, what is flux for the male is flux for the female. For that reason, when I flux the male of the fitting, I also flux the female.

When I do that, I am chemically cleaning the skin of the fitting. I find it peculiar, that is makes good sense to do that on one surface only. Yet, if I were to do that to the one and insert it into the other, it seems obvious that that is doing the fluxing to both.

It is just not quite as direct, nor reliable. The subject of this thread is, "How much flux is too much flux?" I would say, for the purposes of soldering a copper joint, you canÂt do too much  except, that when the job is done, all else is excess. Unfortunately, you donÂt know when the Âthe job is done. Not until it tests good.

If, in fact, fluxing the male part and inserting into the female does provide adequate flux, it is more about technique than chemistry. Both parts need the flux. Being good with applying it with the nipple is a skill. But for those less-practiced, a swab of flux inside the joint is darned good insurance and cheap.

Fluxing a joint is not a definitive notion. The general conditions of cleanliness and degree of oxidation, and the measure of capillary differential all matter. If one wishes to guarantee a successful sweat-joint on the first try, they can introduce flux as if it were solder; and when that is assured, the successful introduction of solder is a given.


Since this reply was written last night, before the above posting, I will include a further reaction.

It appears that the most-skilled of solder-ers are able to both flux the inside diameter blindly with the male part and be assured of sufficient coverage, while getting the spent and excess flux to flow out of the joint and not inward. That is a degree of skill I have never achieved and donÂt expect the average DIYer to gain.

I then assume that perhaps half of the flux I use will end up in the pipes. Like pipe-dope of years gone by and other contaminants that do flow in the stream of potable water, it is not a serious health risk. Flux is neither toxic nor intolerable in the gastric system.

Considering that a purged pipe will remove most of the obnoxious materials immediately, and that continuous use will eventually strip the pipe clean, I consider this to be an issue of minor importance. (Just my opinion, please.)


    Bookmark   November 21, 2006 at 8:34AM
Thank you for reporting this comment. Undo

Now I noticed that someone mentioned flux being an acid base, but do I understand that to be a ph issue, or was Lazypup saying plumbing flux should be acid based? Here in BC and according to what I've read elsewhere, it should be resin I wrong? Soldering, be it plumbing or electronic, wouldn't be the same to me without that piney-fresh smell.

In a pinch, I have found that a scotch-brite, you know, the green plasticy dishwashing scrubbers, work well on cleaning up pipes, maybe not as well as emery cloth, but pretty well.

Based on my limited experience, here are my priorities for a successful soldered joint.

1) ensuring ALL water is prevented from reaching the joint...if it does it will cool the joint and result in a dry joint. Pre-soldered fittings will be cooked and you will need to add solder to make them work. You may think you've drained all the water, but as the pipe heats, more will arrive. You may need to do this to both sides, or just one, but here's the trick.

Wad up a piece of the centre of a slice of bread...yes, bread. stuff it into the pipe, up a few inches, with a dowel or similar. It will stop all water and you will get a lovely smell of toast whilst you solder. When finished, open the furthest tap in the line, remove aerators etc, and flush out completely. If you are soldering into the hot water line, say the supply to the tank, it's probably best you avoid the bread getting in there - say by perhaps using one screw-on or compression fitting... I guess if you can't avoid it, then you drain a fair bit off the tank. It is only bread, so it's not the end of the world and not toxic.

2) Cleaning and fluxing of the joint, as described

3) Correct application of solder AND

4) Avoiding over or under-heating of the joint...when done right, the solder should wick (suck) neatly into the joint, and you will see a beautiful silver ring around the edge of the fitting. To remove the drips - which as far as I know are more a cosmetic issue, a quick wipe with a wadded cloth whilst the solder's hot will fix it. When the solder's set, you can clean off the excess resin with a wet rag and I suppose, some sort of household cleaner, if you don't want sticky pipes, and I suppose it might reduce corrosion.

Flush new work out well. again, without aerators or filters.

    Bookmark   November 21, 2006 at 4:07PM
Thank you for reporting this comment. Undo

There are now available water-soluble fluxes. The NC Plumbing code requires the use of that type flux and also requires the washing of the flux from the exterior of the pipe after soldering. Water flowing through the pipe flushes the interior. The combination of water-soluble flux and lead-free solder does not make soldering easier!

    Bookmark   November 21, 2006 at 5:20PM
Thank you for reporting this comment. Undo

Thanks bus driver, I guess in the long run, one's fairly safe to assume that a good hardware store will have the answer of what's right and legal for your area, provided you ask. I'd assume these days that acid flux is really only for non-plumbing, non-electrical soldering, and with the plethora of cheap oxy-brazing kits (less than $100) and arc welders, there's not so much call for soldering of plain metals these days....or is there?

    Bookmark   November 21, 2006 at 6:43PM
Thank you for reporting this comment. Undo

The "old techniques" work as well today as ever- and I use them where appropriate. I really appreciate the fact that we have more options than ever before. I recall in my younger days longing for better adhesives for metals- we had only the Duco Household Cement. Now we have epoxy, acrylic film adhesives, urethane. I love it!

    Bookmark   November 21, 2006 at 9:25PM
Thank you for reporting this comment. Undo

Despite what regulators would like to see, the cleansing of oxidation from copper fittings is a chemical issue that doesnt have any respect for living documents. So, when you want to remove the inevitable oxidation that occurs when copper is put in the marketplace, you get roughly one choice: acidic reaction.

Resin is not an active chemical. It is a carrier. Within the carrier are the active ingredients. Regardless the good intent, the chemical realities are not negotiable.

So, no matter what procedure is used, it must have the effect of removing the oxidation which would prevent the adhesion of the solder. Scouring the surfaces using mechanical means, such as emery or Scotch-Brite®, does to a high degree expose the base metal to the environment. At this time, the sweat-soldering process can proceed.

Then, just a modest amount of flux will guarantee that the process will continue uninhibited. Of course, for any reclaimed fittings and reworking, the demand changes dramatically.

BTW, Im with Bus_Driver, agreeing that the world is fortunate to have so many new products available thru technology.

I learned a new fact the other day. These super-bright flashlights running LEDs are a remarkable improvement in light. LEDs are developing as a long-life, high-intensity, low power-consumption light source. I can hardly wait for it to be available for area lighting.

What I learned was the technology was born of the necessity to provide the compact and reliable light for night-time personal combat in Iraq. We are reeling from the realities because "necessity is the mother of invention." Im confident that the next generation will be living in a better world, too, given the strong forces of necessities coming from world events.

So, when I get those new lights, I can run the house 24-7 on one peanut per year. Well, not "I" exactly. Maybe my great-grandchildren, or their great-grandchildren, Chin and Chan.


    Bookmark   November 22, 2006 at 10:52AM
Thank you for reporting this comment. Undo

In regards to Brickeyes comments on technology, I could not agree more. I think Brickeye and I are about the same age (59) and thinking back I am amazed at what was science fiction when i was a kid but what is commonplace today. Just a few examples"

When we were in school a word processor was a manual device made of wood and graphite with an eraser on the opposite end..LOL.

When they landed men on the moon complex math was still being done on slide rules, now I have a wristwatch with a built in calculator that can perform functions that were unheard of on mainframe computers in the early to mid 60's.

In Jr.High school every kid dreamed of owning a 6 transistor pocket AM radio receiver. (I actually acquired one by caddying at the local golf course for the whole summer to earn the necessary $36 to buy it.)

minimum wage was $1.55 and top union scale was $5/hr.

Color TV was still in its infancy and most stations did not broadcast color until the early 60's.

FM radio was solely classical and elevator music and of very little interest to young people.

When I entered the Air Force in 1966 I worked with a Univac 1066-II mainframe computer system that had a hard drive which was 10 feet long and weighed over 3 tons, yet it only had 66megs of memory, by contrast I have 80 gigs on this desktop and 60gigs in my laptop, both of which are obsolete by state of the art standards.

While on the subject of laptops, the only laptops devices we had then was a TV tray for dinner....LOL

Cordless tools were totally unheard of.

State of the art automotive safety was a padded dashoard and a seat belt.

I remember when they came out with a digital clock that had rotating flip cards with the numbers on them and we thought that was the rage.

For all you Star Trek fans,,go back and look closely at the first generation scenes, even the spaceship Enterprise did not have LED or Quart Crystal displays.

When we were in school the interstate highways system was still a future dream being discussed in Popular Mechanics Magazine.

A virus made you sick and spam was that cheap nasty canned meat that you mother made you eat whether you liked it or not, suprisingly I acquired a taste for it and still enjoy it occassionally...LOL.

A conferance call was listening in on someone elses phone call on a party line, but don't get caught.

Rich people had a garage door opener, the rest of us were lucky to have a garage and if we did it was doubtful if the old doors would swing properly.

Gas water heaters were not vented to the outside and many had open steel vessels with no insulation. The house I lived in there was no thermocouple on the gas control. I couldn't begin to count how many times we came home to find the pilot had gone out and the house was full of gas.

I am with Brickeye,,I embrace technology.

    Bookmark   November 22, 2006 at 12:20PM
Thank you for reporting this comment. Undo

Wiped lead was useed to make lead pipe joints.
It was a rather tricky way of doing things since pure lead was used for the pipe and the solder.
Molten lead was piured onto the joint and 'wiped' with a heat resistant glove to spread it out and form the joint.
The same method was used on old lead sheathed telephone cables. 'Pulp' insulation (paper) and lead outer jacket with wiped joints (get out the gasoline torch and the ladle). Most of this stuff dates to before WW2, though the use of lead jacketed cable and pulp nsulation continued well into the 1950s in more rural areas of the US (and other countries).
The latest use of lead in DWV I have been able to relibly date was around 1934, but it likely persosted even longer away from major cities.
Lead supply lines seem to have disappeared well before then, though they remain in use in Washington, DC in older parts of the city.

    Bookmark   November 23, 2006 at 8:47PM
Thank you for reporting this comment. Undo

Washington, DC!

But doesnt lead destroy the brain?

Probably, its low exposure. They have water gates there to cover it up.


    Bookmark   November 23, 2006 at 9:59PM
Thank you for reporting this comment. Undo

They are politicians.
How much brain can they have?

    Bookmark   November 24, 2006 at 3:40PM
Thank you for reporting this comment. Undo

My Dad once told me he would sooner have a daugter in a cathouse than a son in politics,,,unfortunately he got both his wishes....LOL

    Bookmark   November 24, 2006 at 4:04PM
Thank you for reporting this comment. Undo

I did some home plumbing the other week to one of the main supply lines that all the water in the house would run through. It seems like since then, the water has tasted a little funny. Is it possible I used too much flux and there was some left inside the pipe that's contaminating our water? Is it harmful to have some flux in drinking water? Will it ever just wash away? Thanks!

    Bookmark   July 26, 2007 at 2:49AM
Thank you for reporting this comment. Undo

Gee .Guess i've been doing it wrong for over 30 years huh pup?

    Bookmark   July 26, 2007 at 9:44PM
Sign Up to comment
More Discussions
troubleshooting thermostatic valve for shower
troubleshooting thermostatic valve, no hot water and...
Warm water mornings on cold line for 30 secs....
We have been living in a home built in 2011 (in Canada)...
Fire Sprinkler
Purchasing a home with an indoor fire sprinkler system....
De-winterize, re-winterize...costs?
My 24 yr old son is buying a 1950 home on a short sale...
Water Softener - calling justalurker
Hopefully you are still around. I had reached out a...
People viewed this after searching for:
© 2015 Houzz Inc. Houzz® The new way to design your home™