What type of flux should not be used when installing copper piping?

Using self-cleaning flux is not advisable for installing copper piping due to its chemical composition that can cause corrosion or other negative reactions with the metal. Self-cleaning flux is designed for specific applications, often involving different types of metals or surfaces that do not include copper.

Acid flux, while sometimes used in various plumbing applications, is particularly harsh and can easily damage the copper if not used cautiously. Lead-free flux is specifically formulated for safe use in plumbing systems to prevent contamination, which is vital for potable water applications, and non-corrosive flux is designed to be gentle on metal surfaces, making it suitable for use with copper.

In summary, the choice not to use self-cleaning flux is rooted in the potential corrosive effects it has on copper, which can lead to failures or leaks in plumbing systems over time.