I had the gas-valve in my thirty-year-old Glow-warm central heating boiler replaced recently
and out of curiosity I dismantled the old one.
I was surprised to find that it was packed with this crystalline debris.
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I know the picture isn't very clear, but the gas main side is on the right, and it seems to methat the contamination has entered via the gas supply.
Incidentally, there are no other gas appliances in the house.
Can anyone enlighten me as to what has caused this?
Graham.