Trouble Soldering

The other day I was trying to install a ball valve on a water heater and could not get the solder to take. I was using a MAPP Gas torch,used lead free solder and flux,used emery cloth on the inside of the valve and inside and out of the copper pipe,heatedthe valve up until the flux was bubbling then tried to put the solder around the joint and it just kept falling off,I should also mention that the pipe was upright and the solder needed to flow up into the joint,any idea what I was doing wrong? I never had that problem before soldering copper pipe,eventually it took hold after 5 attempts. Any advice pertaining to soldering copper pipe would be greatly appreciated. THANKS!

I'm glad I'm not the only one! I'm a DIY'er, and last year tried to put in a water heater expansion tank. Could NOT get a couple of joints to take solder! I used to think I was pretty good a sweat soldering. Now I've kind of lost my nerve. I started to wonder if solder composition has changed, or something ???

One thing that I think may have caused some of my trouble last year was a little bit of water draining from above -- I've since bought some "beads" which look like large Vitamin E capsules and you shove them into a pipe to keep water from spoiling a joint. I plan to try them out one of these weekends.

I suspect you are not getting the fitting hot enough. A valve has more material to heat than a regular fitting, so it does take more time/heat. The solder will "suck up" into the valve when it is hot enough, but I have sometimes soldered short pieces of pipe into the valve first, then used couplers to connect that assembly. Not a very professional approach, but it works if you have room for the extra pieces, and it's sometimes easier to apply the heat to the valve when it is held in a vise where you can get the flame pointed where it should be.

I had a slow drip also, but plugged it with bread. The valve was very hot. In fact I called the store where I had purchased all the supplies and he said to let it cool, before attempting the solder again. After the fifth try of repeating the exact same procedure it held, but it was not pretty!

It's been my experience that solder won't flow if the joint is too hot as well as being too cold. Since you used a hotter gas I think that may be the case here. (Not a pro.)

I too had this trouble recently. I blamed it on the flux. I bought some flux at a local hardware store; it was a water soluble type (not Nokorode brand). I discovered if I overheated it, it would burn and prevent solder flow. Mapp gas is hot, it's what I use too, but it's easy to overheat stuff. I bought some Nokorode flux at Home Depot (also water soluble) but the most expensive one they had ($3.??) I felt it worked much better. That said, next time I'm at a plumbing supply store I'll buy what real plumbers use.

I've use the water based flux. It seemed to work OK, but I prefer the paste type. I use a propane torch, and apply heat just until the solder flows then remove it. I would think you should do the same with Mapp gas, it just wouldn't take as long to heat the joint.

flux

Water soluble flux will "burn" very easily and contaminate the joint, requiring that it be taken apart and cleaned and fluxed again. I am not sure if you had water in the joint or what, but the problem was probably not the MAPP gas, since that is all we ever use. If the joint is not "pretty" depending on what that means, it may not have gotten to the proper point where the solder actually flowed up into the joint.