Chris the builder wrote:used Toms Tip today lol, heres another one... if you're going to go to all the hassle of mains flushing a system, replace all the valves too! re-connected everything, bled rads etc, weeping lock shield olive with no drain cock.... gutted lol.
I make it a habit to ALWAYS wrap PTFE around olives of compression fittings that I have to reuse, as a precaution. Better safe than sorry. Saves me worry of draining down again and again. Though I must accept Rad valves are notorious for little lee way to comfortably wrap PTFE on the suspect olives. In which case, I use a spanner to ''knock'' the olive (by tapping on compression nut end) further out giving better accessibility, then fit valve and tap valve body to push olive back in place, then tighten. Always work for me.