I need to solder some copper tubing that will be used in food preparation. I have of course silver/lead-free solder, but I understand that I might need/want water soluble flux or another type of food-grade flux.

How do I ensure that I can sweat these tubes and not contaminate the fluid with flux?

  1. I would like to use a food-quality flux

  2. I would like to be able to clean the flux

On another web site I saw someone mention acid-washing or acid cleaning.

What should I be doing to ensure my fluid is contaminant-free?

1 Answer 1


All the flux is for is to make the solder wick around the copper more easily to give you a better join.

As long as you're using lead free flux, after you complete the solder joins, run the water for several minutes from each fixture and you're not going to have any worries. People have been using flux w/ copper for decades now w/o any harmful side effects.

  • I am talking about 20 feet of copper tube with about 50 joints in it. The insides of the pipe look black and nasty. There is a film on them. At the very least this imparts a flavor and odor. I will try rinsing with hot water. Thanks
    – Tim
    Commented Aug 24, 2011 at 13:47
  • 1
    That film will be from running your food stuff in the copper pipe- it will require regular cleaning. Most likely organic soap and very hot water- nearly boiling- you need to remember germs and micro bacteria will start to live in there if you don't clean it! Water does not have this problem because it has chlorine, reduced silicates and does not inhibit bacterial growth.
    – Piotr Kula
    Commented Aug 24, 2011 at 15:23

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