This heating system water definitely needs a clean! It looked like the flux needing flushing out or maybe a bacteria process is going on.

The easiest way to connect mains water to flush is though a magnet installed onto the pipework but this system doesn’t have one. Easiest thing for me to do is remove a radiator and connect onto the radiator valves.

Using some fittings from Tesla I’m able to connect hoses from the outside tap using hose lock!

Turn off all the radiators and flush one by one. Can even turn the boiler valves off to stop it going through or open just the boiler and close the rads to flush just the boiler.

Very simple way to flush pipework!