In a flux delivery system, the distances that the flux slurry has to travel is often very short and there is no time for the flux slurry to settle out in the lines or header pipe of the nozzle array. However, if the flux slurry must be conveyed over long distances, to the waste water treatment site at the other end of the plant for instance, then great care must be taken to prevent the lines, drains, pipes and troughs from becoming clogged with settled out flux. The flux slurry is a suspension and unless continuously agitated, the flux will eventually settle out.

If the flux slurry must be conveyed over long distances, it is perhaps better to separate the flux and water with some sort of filter arrangement in the neighborhood of the fluxing station. The solids can be collected near the fluxing station and the particulate free wastewater can then be easily transported.

A second option is to transport the used flux slurries batch-wise (in drums) to the treatment facility or where ever desired. This eliminates all concerns about flux settling out in troughs or other parts of the plumbing system.

In recent years, the topic of what to do with wastewater from fluxing operations has gained a lot of attention in light of heightened environmental awareness and compliance. Years ago, wastewater from cleaning slurry booths, waste flux slurries etc. were simply diluted and dumped down the drain. Some manufacturers are still following this practice, but it is become less and less common. Today, the heat exchanger manufacturers are faced with what to do with wastewater more and more.

Some manufacturers collect the waste slurries and effluent from cleaning out the fluxing stations and allow the flux to settle out. The water phase is then decanted and collected until a sufficient volume is collected. At that point, a waste disposal company is called in to collect and treat the contaminated water. This is an expensive, but in many cases a necessary option. If the collected water is relatively clean and not contaminated with oil, it may be reused to top up flux slurries. The only problem here is that one must be certain that there are no other contaminants in the wastewater other than flux ions. If there are other contaminants (and there almost certainly will be), tests should be performed to ensure that these will not in any way interfere with the brazing process.

Solvay Fluor also developed a continuous process to reuse and recycle wastewater in a fluxing operation. It is based on the principles described above, only in a continuous fashion:
Lauzon, D.C., Swidersky, H.W., “Methods for Eliminating Wastewater from Flux Slurries in Non-Corrosive Flux Brazing”, VTMS 2001-01-1764, pp 649-654, 2001.