Very effective in dealing with limescale but if you have a sensitive nose, be aware! This really catches in the back of your throat, and it made my eyes water a bit, so stand well back when using it. It doesn’t take long though, in the kettle, and left it all sparkling. I didn’t use as much as suggested as otherwise this bottle won’t last long, but it’s an excellent part of my cleaning kit. Good on taps too, wipe over, leave then rinse off. It’s a bit more pricey than buying one off sachets but if you don’t use quite as much each time, it’ll last and it really does work.