When installing branch saddles, it is quite tempting for the installer to cut the hole through the pipe before welding the branch saddle. Do not do this, ever! This will cause the weld to fail, for the following reasons. Whilst the saddle is welding, pressure builds up in the area of the molten plastic. Pressure is a very important function of a successful electrofusion weld. If there is a hole nearby the pressure zone, the pressure will tend to want to move to the point of least resistance, and that will be the hole in the pipe. Due to the hole weakening the "hoop strength" of the pipe, the plastic will tend to soften and sag around the hole. As the molten plastic is moving in that direction, it drags the electrofusion copper coils with it. Eventually the coils start touching each other, which causes an electrical short, the wires that are left in the conductive coil are having too much electricity pumped through them, they get super hot and start burning the plastic, causing a lot of smoke. The amateur video below shows an example of this happening.

.A common misconception for scraping of electrofusion saddles is that you only need to scrape the area on which the saddle is touching the pipe. The correct way to scrape the pipe is to scrape at least 100mm extra either end of the saddle. What happens with scraping a smaller area, is that the scrape area becomes dished, the saddle is touching only the most shallow scraped points and when welded, the wires in the saddle are heating air rather than pipe, which will cause joint failure every time. Be sure to scrape a long and consistent peel with every pass and be sure not to miss any spots.

Immediately after a weld, the pipe and fitting are still soft from the welding process. When using the 'tapping' type of electrofusion saddle, the pipe and fitting must have completely cooled before winding down the self tapper. If the pipe and fitting are still soft, the weld will de-laminate and the hole will not successfully cut through.

# 5 - Tapping Saddle must be correct size