How-to Solder SS Ferrule to Copper Pipe - w/video

[Bob Loblaw]

Here's a quick tutorial on what I have found to be the easiest approach to solder Stainless Steel sanitary fittings to copper pipe. This seems like a pretty basic need for still builders - but I could not find a definitive guide for how to do it. Hopefully other builders will find this useful/helpful. I gathered info from a lot of other threads and other places around the net to put this together. The video is my own but I had some help with the titles... Apologies if it's redundant!

Here is the link to the video: https://vidd.me/e/VM7" onclick="window.open(this.href);return false;" rel="nofollow

Steps
1) Gather materials

• Here's what you need:
  The right Solder/flux:
  - Must be intended to join ferrous/non-ferrous materials.
  - I recommend Harris Staybrite kit. It's a 4% silver solder with a flux that will etch the stainless.
  - There may be other brands, but this one is widely available for less than $10 on the net, or you can pick it up in person at HD for less than $15.
  - Doesn't seem that expensive when you are paying $2-4 an inch for large diameter copper pipe!
  
  Copper pipe: My recommendation is to use M-type copper for a soldered application, as the ID is the best fit for the ferrules. K and L pipes have a smaller ID than the ferrule and DWV is too large.
  
  SS Ferrule(s): These are pretty widely available from brewing supply houses, distilling hardware suppliers, and Amazon or ebay. I recommend using long-neck ferrules as they are easier to square up with the pipe.
  
  Torch: You will need a MAP torch. Propane is not hot enough to work with the silver solder, or a 2"+ joint, for that matter. I have seen others say MAP is not hot enough and that you need Acetylene. This is not my experience.
  
  Emery cloth
  Flux brush

2) Sand and flux as you would an ordinary copper joint: No need to tin the stainless if you have the right flux. The solder will adhere. Just sand the outside of the fitting and the inside of the tube with emery cloth, apply some flux to both, and press fit the two together. If you have the right pipe/fitting combo - the fitting should slide in with relatively little effort. But it might take a bit of deburring and/or convincing with a rubber mallet if the pipe was not cut evenly

3) Fit a ring of solder around the base of the joint: This is the tip I picked up from some Youtube videos. Wrap a length of the solder around the pipe and cut it so that it is the length of the perimeter. Wrap it around the joint where the pipe and ferrule meet. There is usually a little gap there that will bite into the solder a bit. One wrap of the solder seems to be enough. I tried one joint with two wraps and just ended up with a lot of excess solder dripping out of the joint.

4) Heat the Stainless with MAP torch: I heat the stainless with the torch, not the copper. Two reasons for this: 1) The bond on the stainless is critical, and SS it is less heat conductive than copper, so it's important that you apply the flame there and let the heat transfer to the copper. You don't need to worry about getting the SS too hot with a MAP torch; and 2) It's just easier. The flange on the ferrule protects the solder and flux from being burned up by the torch. Others may disagree with this logic - but that is the way I have done it with good results.

If you follow this process, you should be able to sweat a joint in 40-60 seconds. Super fast and easy!