Yes, all Fernox internal leak sealers, such as Fernox Leak Sealer F4, are safe for use with combination and other low water content boilers.
They will not block valves or vents. Leak Sealer F4 Express is recommended for all pressurised systems as this can be added in 30 seconds via a radiator, filling loop or Fernox TF1 Filter, without the need to drain the system.
The Fernox Express Inhibitor Test is available from all major merchants and online plumbing retailers.
Algae in feed and expansion cisterns Leathery skins or films of algae on the surface of expansion cisterns in open vented systems are caused by fungal mould growths. It occurs when the expansion cistern is not properly covered causing dust, insects and spores to be able to enter the water. Algae in feed and expansion cisterns Underfloor heating systems are
One litre of water weighs 1 kg, therefore 2 kg of DS40 System Cleaner per 100 litres of system volume will make a 2% solution.
