Gurgling Noise From Rad When System Drained F&E Empty And Boiler Off

[chloeradhsaw]

My heat only gas boiler is drained from the boiler drain valve - There is no water in the F&E tank. The hot water vented cylinder is removed. So far so good

Twice this evening I heard radiator gurgling noises which frightened the life out of me

I cant seem to reproduce the noise and I cant get to sleep thinking there will be one hell of a flood!

Boiler is off from mains fuse so pump will not run and yet I heard the gurglig noise twice from two different radiators

How can this be possible? Many articles link to airlock in a filled system but have not seen this being mentioned on an empty one!

 

[chloeradhsaw]

Would an open hot water tap / open radiator bleed valve (with system empty) cause gurgling noises?! I cannot think of anything else