How do I get bad joints on copper

[scon1]

I have been using the presoldered joints for a while, usually with no issues. Recently I have had a series of bad joints on a hot water pipe. Am I missing something?
Turn off water, open tap for vent.
I clean the outside of both pipes with wire wool.
Thinly smear flux over the outside of all pipes.
Slide on T joint, to the 3 pipes.
Light Butane / Propane mix torch, get blue flame.
Wave inner blue flame over the T piece, bottom, middle then top.
The bottom and middle joints have the solder bubble out from end.
The top joint remains dry.
The joint is fairly tight against a wall, but I have tried to heat the back first.
After testing, top joint has slight leak. Reheat joint, adding more solder but solder just falls off.
Any ideas?
I have never had a joint so difficult to seal!

 

[nysk2008]

do you mean a fitting like a yorkshire fitting? is it the fitting thats not soldering up properly?

 

[scon1]

Yes - Yorkshire fittings. Especially T's. I switched to Yorkshire's from standard for small jobs as Flux is too expensive to leave behind and has gone missing previously. But recently I get too many dry joints - I don't think I have changed what I do. Usually it is the top of a vertical joint that just will not fill / seal. Usually a quick wave of the torch, the solder bubbles out evenly - leave to cool job done until now!

 

[JCplumb]

Solder ring (yorkshire) fittings do make soldering a little easier but I always add a little solder to them just to be sure.
You can't really re-solder a joint to add more solder after, the solder will just drop off and the solder you melt that's already in the fitting won't re-seal in there properly.
Make sure you clean inside the fitting aswell as outside the pipe, flux just cleans the surfaces and aids with capillary action which is the method that 'coaxes' the liquid solder into the space between pipe and fitting.
Solder will only stick to a clean copper surface.

Or you could use compression or pushfit fittings.

 

[GasmanxxxR1]

You need more flux on that top joint

 

[scon1]

You need more flux on that top joint

I was wondering about flux, when I started out I used to coat liberally but a trainer suggested a smear was enough. To be honest the flux seems to be mainly burnt off before the solder flows. I take on board also cleaning the inside of the joint - I think the bag I am working with is older so could be tarnished. Can I use too much flux? Is more better than not enough - I clean up the joint at the end anyway?

 

[jtsplumbing]

Try using cleaning strip instead of wire wool, you can get strands stuck on pipe/fitting that will cause leak, what flux are you using? is it clean ? may have dirt or wire strands in it. and buying Yorkshire fittings is an expensive way to do jobs, just use odd ones for difficult places, end feed fittings jus a good if done right, try a self cleaning flux.

 

[Ermintrude]

Heat joint and run in some flux put lots of flux on to clear it. Then re heat an solder as normal coating your solder with a dip of flux. Then wipe joint with flux brush to remove ***** from top of molten solder and then wipe with a damp wrag. Assume all the pipes copper clean and metric 15mm or metric 22mm if the top tube is loose in fitting it's an imperial and your better off cutting it back using 3/4 to 22mm straight and then sweating in a new tee.

 

[lame plumber]

getting it too hot and burning the flux, causing a dirty joint that will leak, simples

 

[AWheating]

Another point to consider is do you have an open end for the pressure inside the pipe to escape? Sometimes you will see the solder bubbling alittle as it cools.

 

[snoopy8888]

maybe there is moisture

 

[GasmanxxxR1]

What flux are you using, I find everflux gives the neatest joints but laco would be my second choice. I cant get on with fry's powerflux

 

[SafeGasInstall]

"Practice makes you perfect "

 

[kay-jay]

Problem happen more on 22 than 15 then?

You need some proper gas.

Butane is for decorators......

 

[Ch4 plumbing]

Is the flame too small??
make sure all the pipe and if using old fittings are clean, flux pipe and solder, if your solder drops straight off either your melting the solder with the flame or your not using enough flux!