Re-Solder Copper Pipe After Water Leaked

May 14, 2011 10:58 AM

Help Soldering Water Pipe - AGAIN (please don't recommend shark bites or any shortcuts - I did it last year, and it leaked again, thats why I'm trying to do this the right way).

Ok, well I'm a newbie at soldering, but I've done it a few times before with luck, just not a water pipe.

The copper water pipe in my garage cracked, so I cut out the bad pipe, and got a new small copper pipe with fittings (not threaded) and sweated the pipe, and soldered it (yes, used flux), did everything according to instructions.

However, I guess I didn't solder good enough, and after turning on the water for only a second, a few spots were spraying where the fittings were soldered.

So now, I turned the water off (but left the faucet on so pressure can escape), I've heated up the pipe, and yet when I try to add solder, it just falls off, it won't adhere. Can anyone please help me, tell me there is some way to fix this without having to take the damn pipe off and start all over ??

Thank you in advance!

posted by absolutshrk to home & garden (17 answers total)

I've heated up the pipe, and yet when I try to add solder, it just falls off, it won't adhere

If I remember correctly, the point of using flux is that, as it heats to the point of vaporizing, it "sucks in" solder, making a good seal. I had the same issue when I installed my dishwasher and had to put in an elbow piece that kept leaking, and this is why I suspect, unfortunately, that you'll need to remove the section, reclean the joint areas, reflux well, and resolder.
posted by Blazecock Pileon at 11:08 AM on May 14, 2011

I hope a real plumber shows up here, but as a carpenter for 30 years and a person who plumbed his own home with copper, I would venture to suggest that there was still some water in the old pipe, which turned to steam with the heat and ruined the soldered joint. The old-timer's suggestion that I have followed is to ball up some Wonder Bread (I know, another special trip to the store) and shove it back into each end of the original pipe (to act as a dam) after thoroughly drying out those pipes as far in as you can. This does entail recutting and probably using new connectors, as it is very hard to get all the old solder out so they will fit again. Oh, the Wonder bread is supposed to flush through the system when the water is turned on again, so remove any strainers/aerators from faucets or do not use the bread if there is anything downstream which would be adversely affected by nutrient-free bread.
posted by Hobgoblin at 11:11 AM on May 14, 2011 [2 favorites]

You've got to drain the water out of the pipe before you can solder it. Sounds to me like you are trying to solder a water filled pipe. This sort of thing happens a lot when you do soldering and aren't used to it. Best to repeat the repair, getting it right this time.

Get a small amount of additional pipe and new, appropriate fittings. Cut out the areas you did poorly and dispose of the fittings. Connect everything first for fit, then disassemble it. POLISH all internal and external surfaces you want to solder. Apply flux well and thoroughly. Heat the pipe until you see color change and to the point where the solder will melt WHEN YOU TOUCH THE PIPE WITHOUT THE TORCH APPLIED. At that point, it's ready to accept solder.

Solder at the interface of the things you are joining and if done right, the solder will wick up into the cavity very clearly. If it balls off, you are either tool cold, not fluxed, or the pipe wasn't cleaned. Repeat until you get it right

After several of these episodes, you'll get better. Life is long and plumbing unreliable. Good luck and kudos for doing your own work.
posted by FauxScot at 11:55 AM on May 14, 2011 [2 favorites]

Soldering pipe is only tangentially related to electrical soldering. What are you using for a heat source? You should be using an actual torch, not a soldering iron or something along those lines. You want a lot of heat, enough so that you can sweat the entire joint after removing the heat source and everything's still liquid enough just by touching to the pipes.
posted by odinsdream at 1:05 PM on May 14, 2011

IANYP and if incorrectly done, you can severely burn yourself.

What are you using as your heat source ? As Odinsdream mentioned, you need to use an actual blowtorch, not a soldering iron. Before you apply the solder, you'll need to apply the flame directly to the new piece [in the new joint] and roughly 2-3 inches of the surrounding original pipe for about 15 seconds, until you see the flux smoking quite a bit. Then apply the solder (are you using proper thickness of solder ? you want something a just a little less thick than a USB cord). If I recall correctly with the flame, and don't be afraid of putting too much solder on it.
posted by fizzix at 1:34 PM on May 14, 2011

I'm using a real blow torch, but its just a simple one from Home Depot, its not that powerful, so although it will do the job, I think I have to be patient and really leave it on there for a while to get it hot enough....

The pipe originally had no water, I'm quite sure of that, but I think I didn't do a good enough job soldering, and partially the reason why, its because its right next to the wall and its very tough to get the solder in the back since I can't really see.
posted by absolutshrk at 3:35 PM on May 14, 2011

That's where the magic of capillary action comes in. The pipe and fitting diameters are precisely designed so that, assuming you've heated it properly, applying the solder against one side will cause it to flow all the way around the other due to capillary action. It's easiest if you have access to all sides so you can ensure coverage, but even in tight spaces you can be assured a good joint if you use enough heat and clean the surfaces well before starting.

The easiest way to fuck things up is to not do a superb job cleaning and fluxing, or to stop in the middle of sweating. That causes cold spots and messes up the whole operation.
posted by odinsdream at 5:17 PM on May 14, 2011 [1 favorite]

I know all to well how frustrating this kind of thing can be when you're working on the real joint. I highly recommend, even despite the cost of copper, getting a few extra pieces that you can play with on a bench to get the hang of it before tackling the real thing.
posted by odinsdream at 5:22 PM on May 14, 2011 [2 favorites]

I agree with the others that there is probably still water in the pipes (or else they are not clean enough). You not only have to relieve the pressure but open a faucet below the level of the work to drain the water out. The white bread thing is something I have seen done; there is even a product called Plumber's Bread.
posted by TedW at 7:13 PM on May 14, 2011

Yeah, you're going to have to start over, sorry. You have to have a clean join. Make sure to get that connection screamin' hot, solder flows into joins and toward heat.
posted by pajamazon at 7:17 PM on May 14, 2011

its because its right next to the wall and its very tough to get the solder in the back since I can't really see

Couple tips that helped me out:

• Wear a bicycle helmet light when working in cramped spaces
• Put a black plumber's heat shield behind your work area

The heat shield not only protects the wall from damage and potential fires, but the black background gives usable contrast for the spot you're working on.
posted by Blazecock Pileon at 8:18 PM on May 14, 2011

your comment about a cracked pipe made me think you might have a deeper problem than just a bad solder joint.

If the copper pipe you are dealing with is old enough the pipe may be eroded enough to be too thin to solder well. If you are getting pinhole leaks that spray water perpendicular to the pipe this might be the problem. If you are getting sprays of water parallel with the pipe right at the fitting than you have to re-solder. BTW i am redoing my upstairs bathroom using sharkbyte fittings on copper pipe (fairly new) but have had 0 problems and it really is faster than solder.
posted by bartonlong at 9:02 PM on May 14, 2011

Is there any reason you need to do this repair with solder rather than a flaring tool and threaded compression fittings? Because those are a hell of a lot easier for an unpracticed hand to do properly than soldering is.

Also, are you using silver solder (melts when the pipe is almost red hot) or ordinary lead+tin solder? Lead+tin solder is only good for spouting and downpipes, not for water supply copper, because it's (a) softer and more likely to crack under pressure and (b) toxic.
posted by flabdablet at 6:51 AM on May 15, 2011

Also, are you using silver solder (melts when the pipe is almost red hot) or ordinary lead+tin solder? Lead+tin solder is only good for spouting and downpipes, not for water supply copper, because it's (a) softer and more likely to crack under pressure and (b) toxic.

Is lead+tin solder even generally available anymore? I know even the electronics solder I've purchased doesn't contain lead. The solder available in any plumbing section certainly won't contain lead.
posted by odinsdream at 12:04 PM on May 15, 2011

When this was happening to me last month it was because I was not waiting for the pipe to get hot enough to melt the solder itself and was instead melting the solder with the torch directly. I'd second the suggestion of practicing on a few pieces of pipe to make sure your technique was fine and then try again.
posted by any portmanteau in a storm at 12:45 PM on May 15, 2011

Oatey No. 95 tinning flux helps even amateurs achieve a well sweated joint. This stuff is far more forgiving than regular flux.
posted by caddis at 2:06 PM on May 16, 2011

I recently redid the copper in my bathroom for a new bathtub and one thing my handy-man neighbor stressed to me was to heat the area of the pipe you want the solder to go into. And heat it ridiculously hot. The solder should flow, not have to be coaxed into the joint. Also, once it does start flowing, make sure to circle the joint with it- don't just leave the end of the solder in one place and hope it makes it the whole way around the joint, apply solder in 3 or 4 places.
posted by ish__ at 9:24 PM on May 19, 2011