For detailed instructions on the cleaning of hydronic heating systems using DS40 Descaler & Cleaner please refer to the instruction leaflet inside the box. The product can be poured as a free-flowing powder directly into a powerflushing unit. Alternatively, by pre-dissolving in warm water, the product can be applied, in a sealed system, via a suitable dosing vessel into a radiator. One box (4.41 lbs) is usually sufficient to clean a typical hydronic heating system. For large systems and heavily scaled or sludged systems, additional powder may need to be added. During the early part of the clean, a color change (red-yellow) indicates that the product is exhausted and more powder needs to be added. Once the clean has been completed, add the bottle of System Neutralizer until the solution turns yellow. If the water is still red, more Neutralizer will need to be added. The system must be drained down and flushed several times with fresh water until the water running to drain is clear. After the final drain, it is recommended that the system is inhibited using Fernox Protector F1. Not for use in single feed indirect cylinders, e.g. ‘Primatic’ or similar.