On Monday, 14 November 2016 13:44:19 UTC, Andrew Gabriel wrote:
Added a new radiator at the weekend, to a vented system which I had
recently added new inhibitor. New rad is on top floor and I had laid
on the pipework previously, so only a towel rail needed draining,
and the expansion tank. Not wanting to lose the inhibitor in the
expansion tank, I wanted to plug the outlet. Hunted around, and then
hit on the idea of using the plug of silicone which sets in the nozzle
of a silicone gun tube. Blew the plug out backwards with a compressed
air can, and it worked perfectly.

I have, long ago, successfully used a raw carrot for a similar purpose.

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(c) Dr. S. Lartius, UK. Gmail: dr.s.lartius@