Today I drained my central heating/hot water system. This is a standard vented, pumped S plan with two electric valves and an indirect hot water cylinder, and I'm in UK.
I was lucky enough to have a drain valve underneath ground floor, relatively accessible, see pics:
So I opened it and was able to drain: good! However, upon refilling the system, I found out that that valve will rotate endlessly, and won't guarantee proper isolation: it's stripped.
I was thinking to add an isolating (aka service) valve past the old one, i.e., along the pipe in the bottom part of the images.
Do you think that will work? Or is there a risk that the old valve will leak when the new one is shut? Do you foresee any other possible problem?
Any feedback welcome!