Hi,
As a beginner I was told not to keep removing the safety valve to fill the boiler as it possible to cause wear to the threads, not sure about that but I don’t as a rule fill the boiler that way, just in case. What I do is to use an adapter hose and fill through the blow down valve, either from a water mains tap or use a 12 v caravan pump. The hose is just a bit of pipe with a washer tap and a bit of plastic tube to fit over the blow down valve.
After I have dropped the fire I blow down straight away with a fair pressure all the rubbish in the boiler will tend to be blown out with the steam / water. I also use both blow down valves, I read somewhere that it stops a buildup of deposits on the opposite side of the foundation ring. I also drain the boiler completely after each use and leave all the valves and regulator just cracked open – it stops them from locking up dead tight as the engine cools.
I am assuming here that you are talking about a copper boiler?
Regards,
Chris.