• Dissolves heavy limescale: Sulphamic acid crystals dissolve up to 50% of their own weight in limescale, restoring efficiency to water heaters, cylinders, boiler heat exchangers and metal kettles
• Colour change shows when it's spent: The solution turns from yellow through green to blue as the descaling power is used up, so you know when to drain, rinse and refill
• Mix to the strength you need: Dissolve 250 g to 1 kg in 10 litres of hot water (2.5% to 10%), up to 80°C. The 2kg tub covers repeat jobs or one large system
• Know what it's safe on: Safe on steel, stainless steel, cast iron, copper, brass, PVC, ABS, rubber and polythene. Not for plastic or acrylic kettles, aluminium, zinc, galvanised, chrome-plated or enamelled surfaces
• Use it safely: It fizzes and foams as it works (CO2), so leave space in the vessel. Wear gloves and eye protection, rinse thoroughly afterwards and keep out of reach of children. Fernox code 61027, Belgaqua approved

Fernox DS-3 is a heavy-duty limescale remover made from sulphamic acid crystals with corrosion inhibitors, a colour indicator and non-foaming surfactants. It dissolves up to half its own weight in limescale and restores efficiency to any type of water heater, hot water cylinder, boiler heat exchanger and metal kettle, as well as shower heads and taps soaked in a descaling bath.

Dissolve it in hot water at 250 g to 1 kg per 10 litres, depending on how heavy the scale is, and keep the water below 80°C. Descaling releases carbon dioxide, so the solution will fizz and foam; leave space for this before you start. The solution changes colour from yellow through green to blue as it is used up. Most of the work is done by the time it turns green. When descaling is finished, drain and rinse several times until no traces or odour remain.

DS-3 is safe to use with steel, stainless steel, cast iron, copper, brass, PVC, ABS, rubber, polythene and most plastic pipework. Do not use it on plastic or acrylic kettles and baths, thin-gauge or corroded aluminium, zinc, galvanised steel, chrome-plated or enamelled surfaces, concrete or asbestos. If in doubt, check with the appliance manufacturer.

This product is an irritant: it causes skin and serious eye irritation and is harmful to aquatic life. Wear gloves and eye protection, keep it out of reach of children, and read the label and safety data sheet before use. The 2kg tub has a carry handle and a resealable lid. Fernox product code 61027.