Everbuild Central Heating P12 Noise Silencer is a non-acid based de-scaler which stays permanently in the system with no need to drain or flush. P12 Noise silencer helps to prevent knocking & kettling caused by lime scale & sludge build up. This Everbuild product removes scale & baked on sludge deposits & then prevents scale from reforming. It is compatible with all Everbuild central heating products & will restore heating efficiency & extend the life of the boiler. Everbuild P12 Noise Silencer is suitable for new & existing central heating systems or extensions to existing systems. Size: 1 Litre. (1 litre treats 100 litre system). Store in original container away from frost in a dry area. 36 month shelf life in original unopened container.