Overview
- Facebook user Gemma Lynch said Black Harpic removed heavy brown limescale after being left in the toilet overnight.
- She applied about half a bottle under the rim so it ran into the bowl, then flushed the next morning.
- Her post included before-and-after photos, and coverage notes the claims are based on user experiences rather than independent testing.
- Members of the Mrs Hinch Cleaning Tips group reported similar results, as articles explain brown staining comes from mineral limescale with iron and reactions with urine.
- For a natural option, Smol recommends a citric-acid mix of 2–3 tablespoons per litre of water, adding water before the acid, leaving it in the bowl for a few hours, then flushing.